{"id":489,"date":"2017-10-28T20:38:12","date_gmt":"2017-10-28T12:38:12","guid":{"rendered":"http:\/\/www.chenweikang.top\/?p=489"},"modified":"2017-10-28T20:43:55","modified_gmt":"2017-10-28T12:43:55","slug":"jdk8%e5%8d%81%e5%a4%a7%e6%96%b0%e7%89%b9%e6%80%a7","status":"publish","type":"post","link":"https:\/\/www.chenweikang.top\/?p=489","title":{"rendered":"JDK8 \u5341\u5927\u65b0\u7279\u6027"},"content":{"rendered":"

\u4e00\u3001\u63a5\u53e3\u7684\u9ed8\u8ba4\u65b9\u6cd5<\/h2>\n

\u5728\u63a5\u53e3\u4e2d\u65b0\u589e\u4e86default<\/strong>\u65b9\u6cd5\u548cstatic<\/strong>\u65b9\u6cd5\uff0c\u8fd9\u4e24\u79cd\u65b9\u6cd5\u53ef\u4ee5\u6709\u65b9\u6cd5\u4f53
\n1\u3001static\u65b9\u6cd5<\/strong>
\n\u793a\u4f8b\u4ee3\u7801\uff1a<\/p>\n

public<\/span> interface<\/span> DefalutTest {\r\n    static<\/span> int<\/span> a =5<\/span>;\r\n    default<\/span> void<\/span> defaultMethod(){\r\n        System.out<\/span>.println(\"DefalutTest defalut \u65b9\u6cd5\"<\/span>);\r\n    }\r\n\r\n    int<\/span> sub(int<\/span> a,int<\/span> b);\r\n\r\n    static<\/span> void<\/span> staticMethod() {\r\n        System.out<\/span>.println(\"DefalutTest static \u65b9\u6cd5\"<\/span>);\r\n    }\r\n}<\/code><\/pre>\n
\u63a5\u53e3\u91cc\u7684\u9759\u6001\u65b9\u6cd5\uff0c\u5373static\u4fee\u9970\u7684\u6709\u65b9\u6cd5\u4f53\u7684\u65b9\u6cd5\u4e0d\u4f1a\u88ab\u7ee7\u627f\u6216\u8005\u5b9e\u73b0\uff0c\u4f46\u662f\u9759\u6001\u53d8\u91cf\u4f1a\u88ab\u7ee7\u627f
\n\u4f8b\u5982\uff1a\u6211\u4eec\u6dfb\u52a0\u4e00\u4e2a\u63a5\u53e3DefalutTest\u7684\u5b9e\u73b0\u7c7bDefaultTestImpl<\/p>\n
public<\/span> class<\/span> DefaultTestImpl<\/span> implements<\/span> DefalutTest<\/span>{<\/span>\r\n\r\n    @Override<\/span>\r\n    public<\/span> int<\/span> sub<\/span>(int<\/span> a, int<\/span> b) {\r\n        \/\/ TODO Auto-generated method stub<\/span>\r\n        return<\/span> a-b;\r\n    }\r\n\r\n}<\/code><\/pre>\n
\u5982\u4e0b\u56fe\u6240\u793a\u662f\u8fd9\u4e2a\u5b9e\u73b0\u7c7b\u4e2d\u6240\u6709\u53ef\u8c03\u7528\u7684\u65b9\u6cd5\uff1a
\n\"\u8fd9\u91cc\u5199\u56fe\u7247\u63cf\u8ff0\"
\n\u5728\u8fd9\u4e9b\u65b9\u6cd5\u91cc\u9762\u6211\u4eec\u65e0\u6cd5\u627e\u5230staticMethod\u65b9\u6cd5\uff0c\u5219\u8bf4\u660e\u63a5\u53e3\u4e2d\u7684static\u65b9\u6cd5\u4e0d\u80fd\u88ab\u5b83\u7684\u5b9e\u73b0\u7c7b\u76f4\u63a5\u4f7f\u7528\u3002\u4f46\u662f\u6211\u4eec\u770b\u5230\u4e86defaultMethod\uff0c\u8bf4\u660e\u5b9e\u73b0\u7c7b\u53ef\u4ee5\u76f4\u63a5\u8c03\u7528\u63a5\u53e3\u4e2d\u7684default\u65b9\u6cd5\uff1b
\n\u90a3\u4e48\u5982\u4f55\u4f7f\u7528\u63a5\u53e3\u4e2d\u7684static\u65b9\u6cd5\u5462\uff1f\uff1f\uff1f
\n\u63a5\u53e3.static\u65b9\u6cd5\u8c03\u7528\uff0c\u5982\uff1aDefalutTest.staticMethod();<\/p>\n
    public<\/span> static<\/span> void<\/span> main<\/span>(String[] args) {\r\n        DefaultTestImpl dtl = new<\/span> DefaultTestImpl();\r\n        DefalutTest.staticMethod();\r\n    }<\/code><\/pre>\n
\u5f53\u6211\u4eec\u8bd5\u56fe\u4f7f\u7528\u63a5\u53e3\u7684\u5b50\u63a5\u53e3\u53bb\u8c03\u7528\u7236\u63a5\u53e3\u7684static\u65b9\u6cd5\u662f\uff0c\u6211\u4eec\u53d1\u73b0\uff0c\u65e0\u6cd5\u8c03\u7528\uff0c\u627e\u4e0d\u5230\u65b9\u6cd5\uff1a
\n\"\u8fd9\u91cc\u5199\u56fe\u7247\u63cf\u8ff0\"<\/p>\n
\u7ed3\u8bba\uff1a\u63a5\u53e3\u4e2d\u7684static\u65b9\u6cd5\u4e0d\u80fd\u88ab\u7ee7\u627f\uff0c\u4e5f\u4e0d\u80fd\u88ab\u5b9e\u73b0\u7c7b\u8c03\u7528\uff0c\u53ea\u80fd\u88ab\u81ea\u8eab\u8c03\u7528<\/strong><\/p>\n
2\u3001default\u65b9\u6cd5<\/strong>
\n\u51c6\u5907\u4e00\u4e2a\u5b50\u63a5\u53e3\u7ee7\u627fDefalutTest\u63a5\u53e3<\/p>\n
public<\/span> interface<\/span> SubTest<\/span> extends<\/span> DefalutTest<\/span>{<\/span>\r\n\r\n}<\/code><\/pre>\n
\u51c6\u5907\u4e00\u4e2a\u5b50\u63a5\u53e3\u7684\u5b9e\u73b0\u7c7b<\/p>\n
public<\/span> class<\/span> SubTestImp<\/span> implements<\/span> SubTest<\/span>{<\/span>\r\n\r\n    @Override<\/span>\r\n    public<\/span> int<\/span> sub<\/span>(int<\/span> a, int<\/span> b) {\r\n        \/\/ TODO Auto-generated method stub<\/span>\r\n        return<\/span> a-b;\r\n    }\r\n\r\n}\r\n<\/code><\/pre>\n
\u73b0\u5728\u6211\u4eec\u521b\u5efa\u4e00\u4e2a\u5b50\u63a5\u53e3\u5b9e\u73b0\u7c7b\u5bf9\u8c61\uff0c\u5e76\u8c03\u7528\u5bf9\u8c61\u4e2d\u7684default\u65b9\u6cd5\uff1a<\/p>\n
public<\/span> class<\/span> Main {\r\n\r\n    public<\/span> static<\/span> void<\/span> main<\/span>(String[] args) {\r\n        SubTestImp stl = new<\/span> SubTestImp();\r\n        stl.defaultMethod();\r\n\r\n    }\r\n}<\/code><\/pre>\n
\u6267\u884c\u7ed3\u679c\uff1a
\nDefalutTest defalut \u65b9\u6cd5<\/p>\n
\u7ed3\u8bba1\uff1adefault\u65b9\u6cd5\u53ef\u4ee5\u88ab\u5b50\u63a5\u53e3\u7ee7\u627f\u4ea6\u53ef\u88ab\u5176\u5b9e\u73b0\u7c7b\u6240\u8c03\u7528<\/strong><\/p>\n
\u73b0\u5728\u6211\u4eec\u5728\u5b50\u63a5\u53e3\u4e2d\u91cd\u5199default\u65b9\u6cd5\uff0c\u5728\u8fdb\u884c\u8c03\u7528\uff1a<\/p>\n
public<\/span> interface<\/span> SubTest<\/span> extends<\/span> DefalutTest<\/span>{<\/span>\r\n\r\n    default<\/span> void<\/span> defaultMethod(){\r\n        System.out.println(\"SubTest defalut \u65b9\u6cd5\"<\/span>);\r\n    }\r\n}<\/code><\/pre>\n
\u6267\u884c\u7ed3\u679c\uff1aSubTest defalut \u65b9\u6cd5<\/p>\n
\u7ed3\u8bba2\uff1adefault\u65b9\u6cd5\u88ab\u7ee7\u627f\u65f6\uff0c\u53ef\u4ee5\u88ab\u5b50\u63a5\u53e3\u8986\u5199<\/strong><\/p>\n
\u73b0\u5728\uff0c\u6211\u4eec\u53bb\u9664\u63a5\u53e3\u95f4\u7684\u7ee7\u627f\u5173\u7cfb\uff0c\u5e76\u4f7f\u5f97SubTestImp\u540c\u65f6\u5b9e\u73b0\u7236\u63a5\u53e3\u548c\u5b50\u63a5\u53e3\uff0c\u6211\u4eec\u77e5\u9053\u6b64\u65f6\u7236\u63a5\u53e3\u548c\u5b50\u63a5\u53e3\u4e2d\u5b58\u5728\u540c\u540d\u540c\u53c2\u6570\u7684default\u65b9\u6cd5\uff0c\u8fd9\u4f1a\u600e\u4e48\u6837\uff1f
\n\u5982\u4e0b\u56fe\u6240\u793a\uff0c\u5b9e\u73b0\u7c7b\u62a5\u9519\uff0c\u5b9e\u73b0\u7c7b\u8981\u6c42\u5fc5\u987b\u6307\u5b9a\u4ed6\u8981\u5b9e\u73b0\u90a3\u4e2a\u63a5\u53e3\u4e2d\u7684default\u65b9\u6cd5
\n\"\u8fd9\u91cc\u5199\u56fe\u7247\u63cf\u8ff0\"<\/p>\n
\u7ed3\u8bba3\uff1a\u5982\u679c\u4e00\u4e2a\u7c7b\u5b9e\u73b0\u4e86\u591a\u4e2a\u63a5\u53e3\uff0c\u4e14\u8fd9\u4e9b\u63a5\u53e3\u4e2d\u65e0\u7ee7\u627f\u5173\u7cfb\uff0c\u8fd9\u4e9b\u63a5\u53e3\u4e2d\u82e5\u6709\u76f8\u540c\u7684\uff08\u540c\u540d\uff0c\u540c\u53c2\u6570\uff09\u7684default\u65b9\u6cd5\uff0c\u5219\u63a5\u53e3\u5b9e\u73b0\u7c7b\u4f1a\u62a5\u9519\uff0c\u63a5\u53e3\u5b9e\u73b0\u7c7b\u5fc5\u987b\u901a\u8fc7\u7279\u6b8a\u8bed\u6cd5\u6307\u5b9a\u8be5\u5b9e\u73b0\u7c7b\u8981\u5b9e\u73b0\u90a3\u4e2a\u63a5\u53e3\u7684default\u65b9\u6cd5<\/strong>
\n\u7279\u6b8a\u8bed\u6cd5\uff1a<\u63a5\u53e3>.super.<\u65b9\u6cd5\u540d>([\u53c2\u6570])<\/code>
\n\u793a\u4f8b\u4ee3\u7801\uff1a<\/p>\n
public<\/span> class<\/span> SubTestImp<\/span> implements<\/span> SubTest<\/span>,DefalutTest<\/span>{<\/span>\r\n\r\n    @Override<\/span>\r\n    public<\/span> int<\/span> sub<\/span>(int<\/span> a, int<\/span> b) {\r\n        \/\/ TODO Auto-generated method stub<\/span>\r\n        return<\/span> a-b;\r\n    }\r\n\r\n    @Override<\/span>\r\n    public<\/span> void<\/span> defaultMethod<\/span>() {\r\n        \/\/ TODO Auto-generated method stub<\/span>\r\n        DefalutTest.super<\/span>.defaultMethod();\r\n    }\r\n\r\n}<\/code><\/pre>\n
\u4f7f\u7528\u793a\u4f8b\uff1a<\/p>\n
\/\/\u63a5\u53e3\u4ee3\u7801<\/span>\r\ninterface Formula {\r\n    double<\/span> calculate(int<\/span> a);\r\n    default<\/span> double<\/span> sqrt<\/span>(int<\/span> a) {\r\n        return<\/span> Math.sqrt<\/span>(a);\r\n    }\r\n}\r\n\/\/\u5b9e\u73b0<\/span>\r\nFormula formula = new<\/span> Formula() {\r\n    @Override\r\n    public<\/span> double<\/span> calculate(int<\/span> a) {\r\n        return<\/span> sqrt<\/span>(a * 100<\/span>);\r\n    }\r\n};\r\nformula.calculate(100<\/span>);     \/\/ 100.0<\/span>\r\nformula.sqrt<\/span>(16<\/span>);           \/\/ 4.0<\/span><\/code><\/pre>\n
<\/a>\u4e8c\u3001Lambda \u8868\u8fbe\u5f0f<\/h2>\n
Lambda\u8868\u8fbe\u5f0f\u53ef\u4ee5\u770b\u6210\u662f\u533f\u540d\u5185\u90e8\u7c7b\uff0c\u4f7f\u7528Lambda\u8868\u8fbe\u5f0f\u65f6\uff0c\u63a5\u53e3\u5fc5\u987b\u662f\u51fd\u6570\u5f0f\u63a5\u53e3<\/strong><\/p>\n
\u57fa\u672c\u8bed\u6cd5\uff1a<\/strong><\/p>\n
            <\u51fd\u6570\u5f0f\u63a5\u53e3>  <\u53d8\u91cf\u540d> = (\u53c2\u65701<\/span>\uff0c\u53c2\u65702.<\/span>..)<\/span> -><\/span> {\r\n                    \/\/<\/span>\u65b9\u6cd5\u4f53\r\n        }<\/code><\/pre>\n
\u8bf4\u660e\uff1a<\/strong>
\n(\u53c2\u65701\uff0c\u53c2\u65702\u2026)\u8868\u793a\u53c2\u6570\u5217\u8868\uff1b->\u8868\u793a\u8fde\u63a5\u7b26\uff1b{}\u5185\u90e8\u662f\u65b9\u6cd5\u4f53
\n1\u3001=\u53f3\u8fb9\u7684\u7c7b\u578b\u4f1a\u6839\u636e\u5de6\u8fb9\u7684\u51fd\u6570\u5f0f\u63a5\u53e3\u7c7b\u578b\u81ea\u52a8\u63a8\u65ad\uff1b
\n2\u3001\u5982\u679c\u5f62\u53c2\u5217\u8868\u4e3a\u7a7a\uff0c\u53ea\u9700\u4fdd\u7559()\uff1b
\n3\u3001\u5982\u679c\u5f62\u53c2\u53ea\u67091\u4e2a\uff0c()\u53ef\u4ee5\u7701\u7565\uff0c\u53ea\u9700\u8981\u53c2\u6570\u7684\u540d\u79f0\u5373\u53ef\uff1b
\n4\u3001\u5982\u679c\u6267\u884c\u8bed\u53e5\u53ea\u67091\u53e5\uff0c\u4e14\u65e0\u8fd4\u56de\u503c\uff0c{}\u53ef\u4ee5\u7701\u7565\uff0c\u82e5\u6709\u8fd4\u56de\u503c\uff0c\u5219\u82e5\u60f3\u7701\u53bb{}\uff0c\u5219\u5fc5\u987b\u540c\u65f6\u7701\u7565return\uff0c\u4e14\u6267\u884c\u8bed\u53e5\u4e5f\u4fdd\u8bc1\u53ea\u67091\u53e5\uff1b
\n5\u3001\u5f62\u53c2\u5217\u8868\u7684\u6570\u636e\u7c7b\u578b\u4f1a\u81ea\u52a8\u63a8\u65ad\uff1b
\n6\u3001lambda\u4e0d\u4f1a\u751f\u6210\u4e00\u4e2a\u5355\u72ec\u7684\u5185\u90e8\u7c7b\u6587\u4ef6\uff1b
\n7\u3001lambda\u8868\u8fbe\u5f0f\u82e5\u8bbf\u95ee\u4e86\u5c40\u90e8\u53d8\u91cf\uff0c\u5219\u5c40\u90e8\u53d8\u91cf\u5fc5\u987b\u662ffinal\u7684\uff0c\u82e5\u662f\u5c40\u90e8\u53d8\u91cf\u6ca1\u6709\u52a0final\u5173\u952e\u5b57\uff0c\u7cfb\u7edf\u4f1a\u81ea\u52a8\u6dfb\u52a0\uff0c\u6b64\u540e\u5728\u4fee\u6539\u8be5\u5c40\u90e8\u53d8\u91cf\uff0c\u4f1a\u62a5\u9519\uff1b<\/p>\n
\u793a\u4f8b\u4ee3\u7801\uff1a<\/strong><\/p>\n
public<\/span> interface<\/span> LambdaTest {\r\n\r\n    abstract<\/span> void<\/span> print();\r\n}\r\n\r\npublic<\/span> interface<\/span> LambdaTest2 {\r\n\r\n    abstract<\/span> void<\/span> print(String a);\r\n}\r\n\r\npublic<\/span> interface<\/span> DefalutTest {\r\n\r\n    static<\/span> int<\/span> a =5<\/span>;\r\n    default<\/span> void<\/span> defaultMethod(){\r\n        System.out<\/span>.println(\"DefalutTest defalut \u65b9\u6cd5\"<\/span>);\r\n    }\r\n\r\n    int<\/span> sub(int<\/span> a,int<\/span> b);\r\n\r\n    static<\/span> void<\/span> staticMethod() {\r\n        System.out<\/span>.println(\"DefalutTest static \u65b9\u6cd5\"<\/span>);\r\n    }\r\n}\r\n\r\npublic<\/span> class<\/span> Main {\r\n\r\n    public<\/span> static<\/span> void<\/span> main<\/span>(String[] args) {\r\n        \/\/\u533f\u540d\u5185\u90e8\u7c7b--java8\u4e4b\u524d\u7684\u5b9e\u73b0\u65b9\u5f0f<\/span>\r\n        DefalutTest dt = new<\/span> DefalutTest(){\r\n            @Override\r\n            public<\/span> int<\/span> sub<\/span>(int<\/span> a, int<\/span> b) {\r\n                \/\/ TODO Auto-generated method stub<\/span>\r\n                return<\/span> a-b;\r\n            }\r\n        };\r\n\r\n        \/\/lambda\u8868\u8fbe\u5f0f--\u5b9e\u73b0\u65b9\u5f0f1<\/span>\r\n        DefalutTest dt2 =(a,b)->{\r\n            return<\/span> a-b;\r\n        };\r\n        System.out<\/span>.println(dt2.sub(2<\/span>, 1<\/span>));\r\n\r\n        \/\/lambda\u8868\u8fbe\u5f0f--\u5b9e\u73b0\u65b9\u5f0f2\uff0c\u7701\u7565\u82b1\u62ec\u53f7<\/span>\r\n        DefalutTest dt3 =(a,b)->a-b;\r\n        System.out<\/span>.println(dt3.sub(5<\/span>, 6<\/span>));\r\n\r\n        \/\/\u6d4b\u8bd5final<\/span>\r\n        int<\/span> c = 5<\/span>;\r\n        DefalutTest dt4 =(a,b)->a-c;\r\n        System.out<\/span>.println(dt4.sub(5<\/span>, 6<\/span>));\r\n\r\n        \/\/\u65e0\u53c2\u65b9\u6cd5\uff0c\u5e76\u4e14\u6267\u884c\u8bed\u53e5\u53ea\u67091\u6761<\/span>\r\n        LambdaTest lt = ()-> System.out<\/span>.println(\"\u6d4b\u8bd5\u65e0\u53c2\"<\/span>);\r\n        lt.print();\r\n        \/\/\u53ea\u6709\u4e00\u4e2a\u53c2\u6570\u65b9\u6cd5<\/span>\r\n        LambdaTest2 lt1 = s-> System.out<\/span>.println(s);\r\n        lt1.print(\"\u6709\u4e00\u4e2a\u53c2\u6570\"<\/span>);\r\n    }\r\n}<\/code><\/pre>\n
\u5c40\u90e8\u53d8\u91cf\u4fee\u6539\u62a5\u9519\u5982\u56fe\uff1a
\n\"\u8fd9\u91cc\u5199\u56fe\u7247\u63cf\u8ff0\"
\n\u82e5\u662f\u5f3a\u884c\u4fee\u6539\u4e5f\u65e0\u6cd5\u7f16\u8bd1\u901a\u8fc7<\/p>\n
Lambda\u8868\u8fbe\u5f0f\u5176\u4ed6\u7279\u6027\uff1a<\/em><\/strong><\/p>\n
1\u3001\u5f15\u7528\u5b9e\u4f8b\u65b9\u6cd5\uff1a<\/strong>
\n\u8bed\u6cd5\uff1a<\/strong><\/p>\n
    <\u51fd\u6570\u5f0f\u63a5\u53e3>  <\u53d8\u91cf\u540d> = <\u5b9e\u4f8b>::<\u5b9e\u4f8b\u65b9\u6cd5\u540d>\r\n    \/\/\u8c03\u7528\r\n    <\u53d8\u91cf\u540d>.\u63a5\u53e3\u65b9\u6cd5([\u5b9e\u9645\u53c2\u6570...<\/span>])<\/code><\/pre>\n
\u5c06\u8c03\u7528\u65b9\u6cd5\u65f6\u7684\u4f20\u9012\u7684\u5b9e\u9645\u53c2\u6570\uff0c\u5168\u90e8\u4f20\u9012\u7ed9\u5f15\u7528\u7684\u65b9\u6cd5\uff0c\u6267\u884c\u5f15\u7528\u7684\u65b9\u6cd5\uff1b
\n\u793a\u4f8b\u4ee3\u7801\uff1a<\/strong>
\n\u5982\u6211\u4eec\u5f15\u7528PrintStream\u7c7b\u4e2d\u7684println\u65b9\u6cd5\u3002\u6211\u4eec\u77e5\u9053System\u7c7b\u4e2d\u6709\u4e00\u4e2aPrintStream\u7684\u5b9e\u4f8b\u4e3aout\uff0c\u5f15\u7528\u8be5\u5b9e\u4f8b\u65b9\u6cd5\uff1aSystem.out::println\uff1a<\/p>\n
public<\/span> class<\/span> Main {\r\n\r\n    public<\/span> static<\/span> void<\/span> main<\/span>(String[] args) {\r\n\r\n        LambdaTest2 lt1 = s-> System.out<\/span>.println(s);\r\n        lt1.print(\"\u6709\u4e00\u4e2a\u53c2\u6570\"<\/span>);\r\n\r\n        \/\/\u6539\u5199\u4e3a\uff1a<\/span>\r\n        LambdaTest2 lt2 = System.out<\/span>::println;\r\n        lt2.print(\"\u5b9e\u4f8b\u5f15\u7528\u65b9\u5f0f\u8c03\u7528\"<\/span>);\r\n    }\r\n}<\/code><\/pre>\n
\u5c06lt2\u8c03\u7528\u65f6\u7684\u5b9e\u9645\u53c2\u6570\u4f20\u9012\u7ed9\u4e86PrintStream\u7c7b\u4e2d\u7684println\u65b9\u6cd5\uff0c\u5e76\u8c03\u7528\u8be5\u65b9\u6cd5<\/p>\n
2\u3001\u5f15\u7528\u7c7b\u65b9\u6cd5\uff1a<\/strong>
\n\u8bed\u6cd5\uff1a<\/strong><\/p>\n
    <\u51fd\u6570\u5f0f\u63a5\u53e3>  <\u53d8\u91cf\u540d> = <\u7c7b>::<\u7c7b\u65b9\u6cd5\u540d\u79f0>\r\n    \/\/\u8c03\u7528\r\n    <\u53d8\u91cf\u540d>.\u63a5\u53e3\u65b9\u6cd5([\u5b9e\u9645\u53c2\u6570...<\/span>])<\/code><\/pre>\n
\u5c06\u8c03\u7528\u65b9\u6cd5\u65f6\u7684\u4f20\u9012\u7684\u5b9e\u9645\u53c2\u6570\uff0c\u5168\u90e8\u4f20\u9012\u7ed9\u5f15\u7528\u7684\u65b9\u6cd5\uff0c\u6267\u884c\u5f15\u7528\u7684\u65b9\u6cd5\uff1b
\n\u793a\u4f8b\u4ee3\u7801\uff1a<\/strong>
\n\u6211\u4eec\u53ef\u4ee5\u4ee5\u6570\u7ec4\u6392\u5e8f\u65b9\u5f0f\u4e3a\u4f8b<\/p>\n
public<\/span> interface<\/span> LambdaTest3 {\r\n\r\n    abstract<\/span> void<\/span> sort(int<\/span>[] args);\r\n}\r\n\r\npublic<\/span> class<\/span> Main {\r\n\r\n    public<\/span> static<\/span> void<\/span> main<\/span>(String[] args) {\r\n        List<Integer>  list = new<\/span> ArrayList<Integer>();\r\n        list.add(50<\/span>);\r\n        list.add(18<\/span>);\r\n        list.add(6<\/span>);\r\n        list.add(99<\/span>);\r\n        list.add(32<\/span>);\r\n        System.out<\/span>.println(list.toString()+\"\u6392\u5e8f\u4e4b\u524d\"<\/span>);\r\n        LambdaTest3 lt3 = Collections::sort;\r\n        lt3.sort(list, (a,b) -> {\r\n            return<\/span> a-b;\r\n        });\r\n        System.out<\/span>.println(list.toString()+\"\u6392\u5e8f\u4e4b\u540e\"<\/span>);\r\n    }\r\n}\r\n<\/code><\/pre>\n
\u6267\u884c\u7ed3\u679c\uff1a
\n[50, 18, 6, 99, 32]\u6392\u5e8f\u4e4b\u524d
\n[6, 18, 32, 50, 99]\u6392\u5e8f\u4e4b\u540e<\/p>\n
\u518d\u6765\u770bComparator\u63a5\u53e3\uff0c\u5b83\u5c5e\u4e8e\u51fd\u6570\u5f0f\u63a5\u53e3\uff0c\u6240\u4ee5\u6211\u4eec\u5728Comparator\u5165\u53c2\u65f6\uff0c\u4e5f\u91c7\u53d6\u4e86lambda\u8868\u8fbe\u5f0f\u5199\u6cd5\u3002<\/p>\n
@FunctionalInterface\r\npublic interface Comparator<T<\/span>> {\r\n...<\/span>\r\n...<\/span>\r\n...<\/span>\r\n}<\/code><\/pre>\n
3\u3001\u5f15\u7528\u7c7b\u7684\u5b9e\u4f8b\u65b9\u6cd5\uff1a<\/strong>
\n\u5b9a\u4e49\u3001\u8c03\u7528\u63a5\u53e3\u65f6\uff0c\u9700\u8981\u591a\u4f20\u9012\u4e00\u4e2a\u53c2\u6570\uff0c\u5e76\u4e14\u53c2\u6570\u7684\u7c7b\u578b\u4e0e\u5f15\u7528\u5b9e\u4f8b\u7684\u7c7b\u578b\u4e00\u81f4
\n\u8bed\u6cd5\uff1a<\/strong><\/p>\n
    \/\/\u5b9a\u4e49\u63a5\u53e3\r\n    interface <\u51fd\u6570\u5f0f\u63a5\u53e3>{\r\n        <\u8fd4\u56de\u503c> <\u65b9\u6cd5\u540d>(<\u7c7b><\u7c7b\u540d\u79f0>,[\u5176\u4ed6\u53c2\u6570...<\/span>]); \r\n    }\r\n    <\u51fd\u6570\u5f0f\u63a5\u53e3>  <\u53d8\u91cf\u540d> = <\u7c7b>::<\u7c7b\u5b9e\u4f8b\u65b9\u6cd5\u540d>\r\n    \/\/\u8c03\u7528\r\n    <\u53d8\u91cf\u540d>.\u63a5\u53e3\u65b9\u6cd5(\u7c7b\u7684\u5b9e\u4f8b,[\u5b9e\u9645\u53c2\u6570...<\/span>])<\/code><\/pre>\n
\u5c06\u8c03\u7528\u65b9\u6cd5\u65f6\u7684\u4f20\u9012\u7684\u5b9e\u9645\u53c2\u6570\uff0c\u4ece\u7b2c\u4e8c\u4e2a\u53c2\u6570\u5f00\u59cb\uff08\u7b2c\u4e00\u4e2a\u53c2\u6570\u6307\u5b9a\u7684\u7c7b\u7684\u5b9e\u4f8b\uff09\uff0c\u5168\u90e8\u4f20\u9012\u7ed9\u5f15\u7528\u7684\u65b9\u6cd5\uff0c\u6267\u884c\u5f15\u7528\u7684\u65b9\u6cd5\uff1b
\n\u793a\u4f8b\u4ee3\u7801\uff1a<\/strong><\/p>\n
public<\/span> class<\/span> LambdaClassTest {\r\n\r\n    public<\/span> int<\/span> add<\/span>(int<\/span> a, int<\/span> b){\r\n        System.out<\/span>.println(\"LambdaClassTest\u7c7b\u7684add\u65b9\u6cd5\"<\/span>);\r\n        return<\/span> a+b;\r\n    }\r\n}\r\n\r\npublic<\/span> interface<\/span> LambdaTest4 {\r\n\r\n    abstract<\/span> int<\/span> add(LambdaClassTest lt,int<\/span> a,int<\/span> b);\r\n}\r\n\r\npublic<\/span> class<\/span> Main {\r\n\r\n    public<\/span> static<\/span> void<\/span> main<\/span>(String[] args) {\r\n        LambdaTest4 lt4 = LambdaClassTest::add;\r\n        LambdaClassTest lct = new<\/span> LambdaClassTest();\r\n        System.out<\/span>.println(lt4.add(lct, 5<\/span>, 8<\/span>));\r\n    }\r\n}<\/code><\/pre>\n
4\u3001\u5f15\u7528\u6784\u9020\u5668\u65b9\u6cd5\uff1a<\/strong>
\n\u8bed\u6cd5\uff1a<\/strong><\/p>\n
    <\u51fd\u6570\u5f0f\u63a5\u53e3>  <\u53d8\u91cf\u540d> = <\u7c7b>::<new>\r\n    \/\/\u8c03\u7528\r\n    <\u53d8\u91cf\u540d>.\u63a5\u53e3\u65b9\u6cd5([\u5b9e\u9645\u53c2\u6570...<\/span>])<\/code><\/pre>\n
\u628a\u65b9\u6cd5\u7684\u6240\u6709\u53c2\u6570\u5168\u90e8\u4f20\u9012\u7ed9\u5f15\u7528\u7684\u6784\u9020\u5668\uff0c\u6839\u636e\u53c2\u6570\u7c7b\u578b\u81ea\u52a8\u63a8\u65ad\u8c03\u7528\u7684\u6784\u9020\u5668\u65b9\u6cd5\uff1b
\n\u793a\u4f8b\u4ee3\u7801\uff1a<\/strong><\/p>\n
public<\/span> interface<\/span> LambdaTest5 {\r\n\r\n    abstract<\/span> String creatString(char<\/span>[] c);\r\n}\r\npublic<\/span> class<\/span> Main {\r\n\r\n    public<\/span> static<\/span> void<\/span> main<\/span>(String[] args) {\r\n        LambdaTest5 lt5 = String::new<\/span>;\r\n        System.out<\/span>.println(lt5.creatString(new<\/span> char<\/span>[]{'1'<\/span>,'2'<\/span>,'3'<\/span>,'a'<\/span>}));\r\n    }\r\n}<\/code><\/pre>\n
\u6839\u636e\u4f20\u5165\u7684\u53c2\u6570\u7c7b\u578b\uff0c\u81ea\u52a8\u5339\u914d\u6784\u9020\u51fd\u6570<\/p>\n
<\/a>\u4e09\u3001\u51fd\u6570\u5f0f\u63a5\u53e3<\/h2>\n
\u5982\u679c\u4e00\u4e2a\u63a5\u53e3\u53ea\u6709\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\uff0c\u5219\u8be5\u63a5\u53e3\u79f0\u4e4b\u4e3a\u51fd\u6570\u5f0f\u63a5\u53e3\uff0c\u56e0\u4e3a \u9ed8\u8ba4\u65b9\u6cd5 \u4e0d\u7b97\u62bd\u8c61\u65b9\u6cd5\uff0c\u6240\u4ee5\u4f60\u4e5f\u53ef\u4ee5\u7ed9\u4f60\u7684\u51fd\u6570\u5f0f\u63a5\u53e3\u6dfb\u52a0\u9ed8\u8ba4\u65b9\u6cd5\u3002
\n\u51fd\u6570\u5f0f\u63a5\u53e3\u53ef\u4ee5\u4f7f\u7528Lambda\u8868\u8fbe\u5f0f\uff0clambda\u8868\u8fbe\u5f0f\u4f1a\u88ab\u5339\u914d\u5230\u8fd9\u4e2a\u62bd\u8c61\u65b9\u6cd5\u4e0a
\n\u6211\u4eec\u53ef\u4ee5\u5c06lambda\u8868\u8fbe\u5f0f\u5f53\u4f5c\u4efb\u610f\u53ea\u5305\u542b\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\u7684\u63a5\u53e3\u7c7b\u578b\uff0c\u786e\u4fdd\u4f60\u7684\u63a5\u53e3\u4e00\u5b9a\u8fbe\u5230\u8fd9\u4e2a\u8981\u6c42\uff0c\u4f60\u53ea\u9700\u8981\u7ed9\u4f60\u7684\u63a5\u53e3\u6dfb\u52a0 @FunctionalInterface \u6ce8\u89e3\uff0c\u7f16\u8bd1\u5668\u5982\u679c\u53d1\u73b0\u4f60\u6807\u6ce8\u4e86\u8fd9\u4e2a\u6ce8\u89e3\u7684\u63a5\u53e3\u6709\u591a\u4e8e\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\u7684\u65f6\u5019\u4f1a\u62a5\u9519\u7684<\/p>\n
\u793a\u4f8b\u4ee3\u7801\uff1a<\/strong><\/p>\n
@FunctionalInterface\r\ninterface<\/span> Converter<F, T> {\r\n    T convert(F from<\/span>);\r\n}\r\nConverter<String, Integer> converter = (from<\/span>) -> Integer.valueOf(from<\/span>);\r\nInteger converted = converter.convert(\"123\"<\/span>);\r\nSystem.out<\/span>.println(converted);    \/\/ 123<\/span><\/code><\/pre>\n
<\/a>\u4e94\u3001Lambda \u4f5c\u7528\u57df<\/h2>\n
\u5728lambda\u8868\u8fbe\u5f0f\u4e2d\u8bbf\u95ee\u5916\u5c42\u4f5c\u7528\u57df\u548c\u8001\u7248\u672c\u7684\u533f\u540d\u5bf9\u8c61\u4e2d\u7684\u65b9\u5f0f\u5f88\u76f8\u4f3c\u3002\u4f60\u53ef\u4ee5\u76f4\u63a5\u8bbf\u95ee\u6807\u8bb0\u4e86final\u7684\u5916\u5c42\u5c40\u90e8\u53d8\u91cf\uff0c\u6216\u8005\u5b9e\u4f8b\u7684\u5b57\u6bb5\u4ee5\u53ca\u9759\u6001\u53d8\u91cf\u3002<\/p>\n
<\/a>\u516d\u3001\u8bbf\u95ee\u5c40\u90e8\u53d8\u91cf<\/h2>\n
\u6211\u4eec\u53ef\u4ee5\u76f4\u63a5\u5728lambda\u8868\u8fbe\u5f0f\u4e2d\u8bbf\u95ee\u5916\u5c42\u7684\u5c40\u90e8\u53d8\u91cf\uff0c\u4f46\u662f\u8be5\u5c40\u90e8\u53d8\u91cf\u5fc5\u987b\u662ffinal\u7684\uff0c\u5373\u4f7f\u6ca1\u6709\u52a0final\u5173\u952e\u5b57\uff0c\u4e4b\u540e\u6211\u4eec\u65e0\u8bba\u5728\u54ea\uff08lambda\u8868\u8fbe\u5f0f\u5185\u90e8\u6216\u5916\u90e8\uff09\u4fee\u6539\u8be5\u53d8\u91cf\uff0c\u5747\u62a5\u9519\u3002<\/p>\n
<\/a>\u4e03\u3001\u8bbf\u95ee\u5bf9\u8c61\u5b57\u6bb5\u4e0e\u9759\u6001\u53d8\u91cf<\/h2>\n
lambda\u5185\u90e8\u5bf9\u4e8e\u5b9e\u4f8b\u7684\u5b57\u6bb5\u4ee5\u53ca\u9759\u6001\u53d8\u91cf\u662f\u5373\u53ef\u8bfb\u53c8\u53ef\u5199\u3002\u8be5\u884c\u4e3a\u548c\u533f\u540d\u5bf9\u8c61\u662f\u4e00\u81f4\u7684\uff1b<\/p>\n
\u793a\u4f8b\u4ee3\u7801\uff1a<\/strong><\/p>\n
class<\/span> Lambda4<\/span> {<\/span>\r\n    static int outerStaticNum;\r\n    int outerNum;\r\n    void<\/span> testScopes() {\r\n        Converter<Integer, String> stringConverter1<\/span> = (from)<\/span> -><\/span> {\r\n            outerNum = 23<\/span>;\r\n            return<\/span> String.valueOf(from);\r\n        };\r\n        Converter<Integer, String> stringConverter2<\/span> = (from)<\/span> -><\/span> {\r\n            outerStaticNum = 72<\/span>;\r\n            return<\/span> String.valueOf(from);\r\n        };\r\n    }\r\n}<\/code><\/pre>\n
<\/a>\u516b\u3001\u8bbf\u95ee\u63a5\u53e3\u7684\u9ed8\u8ba4\u65b9\u6cd5<\/h2>\n
Predicate\u63a5\u53e3<\/strong>
\nPredicate \u63a5\u53e3\u53ea\u6709\u4e00\u4e2a\u53c2\u6570\uff0c\u8fd4\u56deboolean\u7c7b\u578b\u3002\u8be5\u63a5\u53e3\u5305\u542b\u591a\u79cd\u9ed8\u8ba4\u65b9\u6cd5\u6765\u5c06Predicate\u7ec4\u5408\u6210\u5176\u4ed6\u590d\u6742\u7684\u903b\u8f91\uff08\u6bd4\u5982\uff1a\u4e0e\uff0c\u6216\uff0c\u975e\uff09\uff1a<\/p>\n
    public static void main(String[] args) {\r\n        Predicate<String> predicate = (s) -> s.length<\/span>() > 0<\/span>;<\/span>\r\n        System.out<\/span>.println<\/span>(predicate.test<\/span>(\"foo\"<\/span>));              \/\/ true<\/span>\r\n        System.out<\/span>.println<\/span>(predicate.negate<\/span>().test<\/span>(\"foo\"<\/span>));     \/\/ false<\/span>\r\n        Predicate<Boolean> nonNull = Objects::nonNull;<\/span>\r\n        Predicate<Boolean> isNull = Objects::isNull;<\/span>\r\n        Predicate<String> isEmpty = String::isEmpty;<\/span>\r\n        Predicate<String> isNotEmpty = isEmpty.negate<\/span>();<\/span>\r\n        System.out<\/span>.println<\/span>(nonNull.test<\/span>(null));<\/span>\r\n        System.out<\/span>.println<\/span>(isNull.test<\/span>(null));<\/span>\r\n        System.out<\/span>.println<\/span>(isEmpty.test<\/span>(\"sss\"<\/span>));<\/span>\r\n        System.out<\/span>.println<\/span>(isNotEmpty.test<\/span>(\"\"<\/span>));<\/span>\r\n    }<\/code><\/pre>\n
\u8fd0\u884c\u7ed3\u679c\uff1a<\/strong>
\ntrue
\nfalse
\nfalse
\ntrue
\nfalse
\nfalse<\/p>\n
Function \u63a5\u53e3<\/strong>
\nFunction \u63a5\u53e3\u6709\u4e00\u4e2a\u53c2\u6570\u5e76\u4e14\u8fd4\u56de\u4e00\u4e2a\u7ed3\u679c\uff0c\u5e76\u9644\u5e26\u4e86\u4e00\u4e9b\u53ef\u4ee5\u548c\u5176\u4ed6\u51fd\u6570\u7ec4\u5408\u7684\u9ed8\u8ba4\u65b9\u6cd5\uff08compose, andThen\uff09\uff1a<\/p>\n
        Function<String, Integer> toInteger = Integer::valueOf;<\/span>\r\n        System.out<\/span>.println<\/span>(toInteger.apply<\/span>(\"123\"<\/span>).getClass<\/span>());<\/span>\r\n        Function<String, Object> toInteger2 = toInteger.andThen<\/span>(String::valueOf);<\/span>\r\n        System.out<\/span>.println<\/span>(toInteger2.apply<\/span>(\"123\"<\/span>).getClass<\/span>());<\/span><\/code><\/pre>\n
\u8f93\u51fa\uff1a
\nclass java.lang.Integer
\nclass java.lang.String<\/p>\n
Supplier \u63a5\u53e3<\/strong>
\nSupplier \u63a5\u53e3\u8fd4\u56de\u4e00\u4e2a\u4efb\u610f\u8303\u578b\u7684\u503c\uff0c\u548cFunction\u63a5\u53e3\u4e0d\u540c\u7684\u662f\u8be5\u63a5\u53e3\u6ca1\u6709\u4efb\u4f55\u53c2\u6570<\/p>\n
Supplier<Person> personSupplier = Person::new<\/span>;\r\npersonSupplier.get<\/span>();   \/\/ new Person<\/span><\/code><\/pre>\n
Consumer \u63a5\u53e3<\/strong><\/p>\n
Consumer \u63a5\u53e3\u8868\u793a\u6267\u884c\u5728\u5355\u4e2a\u53c2\u6570\u4e0a\u7684\u64cd\u4f5c\u3002\u63a5\u53e3\u53ea\u6709\u4e00\u4e2a\u53c2\u6570\uff0c\u4e14\u65e0\u8fd4\u56de\u503c<\/p>\n
        Supplier<LambdaClassTest> personSupplier = LambdaClassTest::new;<\/span>\r\n        Consumer<LambdaClassTest> greeter = (lt) -> System.out<\/span>.println<\/span>(\"Hello, \"<\/span> + lt.getTest<\/span>());<\/span>\r\n        greeter.accept<\/span>(personSupplier.get<\/span>());<\/span><\/code><\/pre>\n
Comparator \u63a5\u53e3<\/strong><\/p>\n
Comparator \u662f\u8001Java\u4e2d\u7684\u7ecf\u5178\u63a5\u53e3\uff0c Java 8\u5728\u6b64\u4e4b\u4e0a\u6dfb\u52a0\u4e86\u591a\u79cd\u9ed8\u8ba4\u65b9\u6cd5\uff1a<\/p>\n
Comparator<Person> comparator = (p1, p2) -> p1.firstName<\/span>.compareTo<\/span>(p2.firstName<\/span>);<\/span>\r\nPerson p1 = new Person(\"John\"<\/span>, \"Doe\"<\/span>);<\/span>\r\nPerson p2 = new Person(\"Alice\"<\/span>, \"Wonderland\"<\/span>);<\/span>\r\ncomparator.compare<\/span>(p1, p2);             \/\/ > 0<\/span>\r\ncomparator.reversed<\/span>().compare<\/span>(p1, p2);  \/\/ < 0<\/span><\/code><\/pre>\n
Optional \u63a5\u53e3<\/strong><\/p>\n
Optional \u4e0d\u662f\u51fd\u6570\u662f\u63a5\u53e3\uff0c\u8fd9\u662f\u4e2a\u7528\u6765\u9632\u6b62NullPointerException\u5f02\u5e38\u7684\u8f85\u52a9\u7c7b\u578b\uff0c\u8fd9\u662f\u4e0b\u4e00\u5c4a\u4e2d\u5c06\u8981\u7528\u5230\u7684\u91cd\u8981\u6982\u5ff5\uff0c\u73b0\u5728\u5148\u7b80\u5355\u7684\u770b\u770b\u8fd9\u4e2a\u63a5\u53e3\u80fd\u5e72\u4ec0\u4e48\uff1a
\nOptional \u88ab\u5b9a\u4e49\u4e3a\u4e00\u4e2a\u7b80\u5355\u7684\u5bb9\u5668\uff0c\u5176\u503c\u53ef\u80fd\u662fnull\u6216\u8005\u4e0d\u662fnull\u3002\u5728Java 8\u4e4b\u524d\u4e00\u822c\u67d0\u4e2a\u51fd\u6570\u5e94\u8be5\u8fd4\u56de\u975e\u7a7a\u5bf9\u8c61\u4f46\u662f\u5076\u5c14\u5374\u53ef\u80fd\u8fd4\u56de\u4e86null\uff0c\u800c\u5728Java 8\u4e2d\uff0c\u4e0d\u63a8\u8350\u4f60\u8fd4\u56denull\u800c\u662f\u8fd4\u56deOptional\u3002<\/p>\n
Optional<String> optional = Optional.of<\/span>(\"bam\"<\/span>);\r\noptional.isPresent();           \/\/<\/span> true<\/span>\r\noptional.get();                 \/\/<\/span> \"bam\"<\/span>\r\noptional.orElse(\"fallback\"<\/span>);    \/\/<\/span> \"bam\"<\/span>\r\noptional.ifPresent((s) -> System.out.println(s.charAt(0<\/span>)))<\/span>;     \/\/ \"b<\/span>\"<\/span><\/code><\/pre>\n
Stream \u63a5\u53e3 \u91cd\u8981\uff01\uff01\uff01<\/strong><\/p>\n
\u521b\u5efastream\u2013\u901a\u8fc7of\u65b9\u6cd5<\/strong><\/p>\n
Stream<Integer<\/span>> integerStream = Stream.of<\/span>(1<\/span>, 2<\/span>, 3<\/span>, 5<\/span>);\r\nStream<String<\/span>> stringStream = Stream.of<\/span>(\"taobao\"<\/span>);<\/code><\/pre>\n
\u521b\u5efastream\u2013\u901a\u8fc7generator\u65b9\u6cd5<\/strong>
\n\u751f\u6210\u4e00\u4e2a\u65e0\u9650\u957f\u5ea6\u7684Stream\uff0c\u5176\u5143\u7d20\u7684\u751f\u6210\u662f\u901a\u8fc7\u7ed9\u5b9a\u7684Supplier\uff08\u8fd9\u4e2a\u63a5\u53e3\u53ef\u4ee5\u770b\u6210\u4e00\u4e2a\u5bf9\u8c61\u7684\u5de5\u5382\uff0c\u6bcf\u6b21\u8c03\u7528\u8fd4\u56de\u4e00\u4e2a\u7ed9\u5b9a\u7c7b\u578b\u7684\u5bf9\u8c61\uff09<\/p>\n
Stream.generate(new<\/span> Supplier<Double>() {\r\n\r\n    @Override<\/span>\r\n\r\n    public Double get() {\r\n\r\n        return<\/span> Math.random();\r\n\r\n    }\r\n\r\n});\r\n\r\nStream.generate(() -> Math.random())<\/span>;\r\n\r\nStream<\/span>.generate<\/span>(Math::random)<\/span>;<\/span><\/code><\/pre>\n
\u4e09\u6761\u8bed\u53e5\u7684\u4f5c\u7528\u90fd\u662f\u4e00\u6837\u7684\uff0c\u53ea\u662f\u4f7f\u7528\u4e86lambda\u8868\u8fbe\u5f0f\u548c\u65b9\u6cd5\u5f15\u7528\u7684\u8bed\u6cd5\u6765\u7b80\u5316\u4ee3\u7801\u3002\u6bcf\u6761\u8bed\u53e5\u5176\u5b9e\u90fd\u662f\u751f\u6210\u4e00\u4e2a\u65e0\u9650\u957f\u5ea6\u7684Stream\uff0c\u5176\u4e2d\u503c\u662f\u968f\u673a\u7684\u3002\u8fd9\u4e2a\u65e0\u9650\u957f\u5ea6Stream\u662f\u61d2\u52a0\u8f7d\uff0c\u4e00\u822c\u8fd9\u79cd\u65e0\u9650\u957f\u5ea6\u7684Stream\u90fd\u4f1a\u914d\u5408Stream\u7684limit()\u65b9\u6cd5\u6765\u7528\u3002<\/p>\n
\u521b\u5efastream\u2013\u901a\u8fc7iterate\u65b9\u6cd5<\/strong>
\n\u4e5f\u662f\u751f\u6210\u65e0\u9650\u957f\u5ea6\u7684Stream\uff0c\u548cgenerator\u4e0d\u540c\u7684\u662f\uff0c\u5176\u5143\u7d20\u7684\u751f\u6210\u662f\u91cd\u590d\u5bf9\u7ed9\u5b9a\u7684\u79cd\u5b50\u503c(seed)\u8c03\u7528\u7528\u6237\u6307\u5b9a\u51fd\u6570\u6765\u751f\u6210\u7684\u3002\u5176\u4e2d\u5305\u542b\u7684\u5143\u7d20\u53ef\u4ee5\u8ba4\u4e3a\u662f\uff1aseed\uff0cf(seed),f(f(seed))\u65e0\u9650\u5faa\u73af
\nStream.iterate(1, item -> item + 1).limit(10).forEach(System.out::println);
\n\u8fd9\u6bb5\u4ee3\u7801\u5c31\u662f\u5148\u83b7\u53d6\u4e00\u4e2a\u65e0\u9650\u957f\u5ea6\u7684\u6b63\u6574\u6570\u96c6\u5408\u7684Stream\uff0c\u7136\u540e\u53d6\u51fa\u524d10\u4e2a\u6253\u5370\u3002\u5343\u4e07\u8bb0\u4f4f\u4f7f\u7528limit\u65b9\u6cd5\uff0c\u4e0d\u7136\u4f1a\u65e0\u9650\u6253\u5370\u4e0b\u53bb\u3002<\/p>\n
\u901a\u8fc7Collection\u5b50\u7c7b\u83b7\u53d6Stream<\/strong><\/p>\n
\r\npublic<\/span> interface<\/span> Collection<\/span><E<\/span>> extends<\/span> Iterable<\/span><E<\/span>> {<\/span>\r\n\r\n    \/\/\u5176\u4ed6\u65b9\u6cd5\u7701\u7565<\/span>\r\n\r\n    default<\/span> Stream<E> stream() {\r\n\r\n        return<\/span> StreamSupport.stream(spliterator(), false<\/span>);\r\n\r\n    }\r\n\r\n}<\/code><\/pre>\n
java.util.Stream \u8868\u793a\u80fd\u5e94\u7528\u5728\u4e00\u7ec4\u5143\u7d20\u4e0a\u4e00\u6b21\u6267\u884c\u7684\u64cd\u4f5c\u5e8f\u5217\u3002Stream \u64cd\u4f5c\u5206\u4e3a\u4e2d\u95f4\u64cd\u4f5c\u6216\u8005\u6700\u7ec8\u64cd\u4f5c\u4e24\u79cd\uff0c\u6700\u7ec8\u64cd\u4f5c\u8fd4\u56de\u4e00\u7279\u5b9a\u7c7b\u578b\u7684\u8ba1\u7b97\u7ed3\u679c\uff0c\u800c\u4e2d\u95f4\u64cd\u4f5c\u8fd4\u56deStream\u672c\u8eab\uff0c\u8fd9\u6837\u4f60\u5c31\u53ef\u4ee5\u5c06\u591a\u4e2a\u64cd\u4f5c\u4f9d\u6b21\u4e32\u8d77\u6765\u3002Stream \u7684\u521b\u5efa\u9700\u8981\u6307\u5b9a\u4e00\u4e2a\u6570\u636e\u6e90\uff0c\u6bd4\u5982 java.util.Collection\u7684\u5b50\u7c7b\uff0cList\u6216\u8005Set\uff0c Map\u4e0d\u652f\u6301\u3002Stream\u7684\u64cd\u4f5c\u53ef\u4ee5\u4e32\u884c\u6267\u884c\u6216\u8005\u5e76\u884c\u6267\u884c\u3002<\/p>\n
Java 8\u6269\u5c55\u4e86\u96c6\u5408\u7c7b\uff0c\u53ef\u4ee5\u901a\u8fc7 Collection.stream() \u6216\u8005 Collection.parallelStream() \u6765\u521b\u5efa\u4e00\u4e2aStream\u3002
\nStream\u6709\u4e32\u884c\u548c\u5e76\u884c\u4e24\u79cd\uff0c\u4e32\u884cStream\u4e0a\u7684\u64cd\u4f5c\u662f\u5728\u4e00\u4e2a\u7ebf\u7a0b\u4e2d\u4f9d\u6b21\u5b8c\u6210\uff0c\u800c\u5e76\u884cStream\u5219\u662f\u5728\u591a\u4e2a\u7ebf\u7a0b\u4e0a\u540c\u65f6\u6267\u884c\u3002<\/p>\n
\u4e0b\u9762\u7684\u4f8b\u5b50\u5c55\u793a\u4e86\u662f\u5982\u4f55\u901a\u8fc7\u5e76\u884cStream\u6765\u63d0\u5347\u6027\u80fd\uff1a
\n\u9996\u5148\u6211\u4eec\u521b\u5efa\u4e00\u4e2a\u6ca1\u6709\u91cd\u590d\u5143\u7d20\u7684\u5927\u8868\uff1a<\/p>\n
int<\/span> max<\/span> = 1000000<\/span>;\r\nList<String> values = new ArrayList<>(max<\/span>);\r\nfor<\/span> (int<\/span> i = 0<\/span>; i < max<\/span>; i++) {\r\n    UUID uuid = UUID.randomUUID();\r\n    values.add(uuid.toString());\r\n}<\/code><\/pre>\n
\u7136\u540e\u6211\u4eec\u8ba1\u7b97\u4e00\u4e0b\u6392\u5e8f\u8fd9\u4e2aStream\u8981\u8017\u65f6\u591a\u4e45\uff0c
\n\u4e32\u884c\u6392\u5e8f\uff1a<\/strong><\/p>\n
long t0 = System.nanoTime<\/span>();<\/span>\r\nlong count = values.stream<\/span>().sorted<\/span>().count<\/span>();<\/span>\r\nSystem.out<\/span>.println<\/span>(count);<\/span>\r\nlong t1 = System.nanoTime<\/span>();<\/span>\r\nlong millis = TimeUnit.NANOSECONDS<\/span>.toMillis<\/span>(t1 - t0);<\/span>\r\nSystem.out<\/span>.println<\/span>(String.format<\/span>(\"sequential sort took: %d ms\"<\/span>, millis));<\/span><\/code><\/pre>\n
\/\/ \u4e32\u884c\u8017\u65f6: 899 ms
\n\u5e76\u884c\u6392\u5e8f\uff1a<\/strong><\/p>\n
long t0 = System.nanoTime<\/span>();<\/span>\r\nlong count = values.parallelStream<\/span>().sorted<\/span>().count<\/span>();<\/span>\r\nSystem.out<\/span>.println<\/span>(count);<\/span>\r\nlong t1 = System.nanoTime<\/span>();<\/span>\r\nlong millis = TimeUnit.NANOSECONDS<\/span>.toMillis<\/span>(t1 - t0);<\/span>\r\nSystem.out<\/span>.println<\/span>(String.format<\/span>(\"parallel sort took: %d ms\"<\/span>, millis));<\/span><\/code><\/pre>\n
\/\/ \u5e76\u884c\u6392\u5e8f\u8017\u65f6: 472 ms
\n\u4e0a\u9762\u4e24\u4e2a\u4ee3\u7801\u51e0\u4e4e\u662f\u4e00\u6837\u7684\uff0c\u4f46\u662f\u5e76\u884c\u7248\u7684\u5feb\u4e8650%\u4e4b\u591a\uff0c\u552f\u4e00\u9700\u8981\u505a\u7684\u6539\u52a8\u5c31\u662f\u5c06stream()\u6539\u4e3aparallelStream()<\/strong>\uff1b<\/p>\n
stream\u7684\u5176\u4ed6\u5e94\u7528\uff1a<\/strong>
\n1\u3001count()\u3001max()\u3001min()<\/strong>\u65b9\u6cd5<\/p>\n
import java.util<\/span>.ArrayList<\/span>;<\/span>\r\nimport java.util<\/span>.List<\/span>;<\/span>\r\n\r\npublic class Main {\r\n\r\n    public static void main(String[] args) {\r\n        List<Integer> collection = new ArrayList<Integer>();<\/span>\r\n        collection.add<\/span>(14<\/span>);<\/span>\r\n        collection.add<\/span>(5<\/span>);<\/span>\r\n        collection.add<\/span>(43<\/span>);<\/span>\r\n        collection.add<\/span>(89<\/span>);<\/span>\r\n        collection.add<\/span>(64<\/span>);<\/span>\r\n        collection.add<\/span>(112<\/span>);<\/span>\r\n        collection.add<\/span>(55<\/span>);<\/span>\r\n        collection.add<\/span>(55<\/span>);<\/span>\r\n        collection.add<\/span>(58<\/span>);<\/span>\r\n        \/\/list\u957f\u5ea6\r\n        System.out<\/span>.println<\/span>(collection.parallelStream<\/span>().count<\/span>());<\/span>\r\n\r\n        \/\/\u6c42\u6700\u5927\u503c,\u8fd4\u56deOption,\u901a\u8fc7Option.get<\/span>()\u83b7\u53d6\u503c\r\n        System.out<\/span>.println<\/span>(collection.parallelStream<\/span>().max<\/span>((a,b)->{return a-b;}).get());<\/span>\r\n\r\n        \/\/\u6c42\u6700\u5c0f\u503c,\u8fd4\u56deOption,\u901a\u8fc7Option.get<\/span>()\u83b7\u53d6\u503c\r\n        System.out<\/span>.println<\/span>(collection.parallelStream<\/span>().min<\/span>((a,b)->{return a-b;}).get());<\/span>\r\n\r\n    }\r\n}<\/code><\/pre>\n
2\u3001Filter \u8fc7\u6ee4\u65b9\u6cd5<\/strong>
\n\u8fc7\u6ee4\u901a\u8fc7\u4e00\u4e2apredicate\u63a5\u53e3\u6765\u8fc7\u6ee4\u5e76\u53ea\u4fdd\u7559\u7b26\u5408\u6761\u4ef6\u7684\u5143\u7d20\uff0c\u8be5\u64cd\u4f5c\u5c5e\u4e8e\u4e2d\u95f4\u64cd\u4f5c\u3002<\/p>\n
import java.util<\/span>.ArrayList<\/span>;<\/span>\r\nimport java.util<\/span>.List<\/span>;<\/span>\r\n\r\npublic class Main {\r\n\r\n    public static void main(String[] args) {\r\n        List<Integer> collection = new ArrayList<Integer>();<\/span>\r\n        collection.add<\/span>(14<\/span>);<\/span>\r\n        collection.add<\/span>(5<\/span>);<\/span>\r\n        collection.add<\/span>(43<\/span>);<\/span>\r\n        collection.add<\/span>(89<\/span>);<\/span>\r\n        collection.add<\/span>(64<\/span>);<\/span>\r\n        collection.add<\/span>(112<\/span>);<\/span>\r\n        collection.add<\/span>(55<\/span>);<\/span>\r\n        collection.add<\/span>(55<\/span>);<\/span>\r\n        collection.add<\/span>(58<\/span>);<\/span>\r\n        Long count =collection.stream<\/span>().filter<\/span>(num -> num!=null).\r\n                filter(num -> num.intValue<\/span>()>50<\/span>).count<\/span>();<\/span>\r\n        System.out<\/span>.println<\/span>(count);<\/span>\r\n    }\r\n}<\/code><\/pre>\n
3\u3001distinct\u65b9\u6cd5<\/strong>
\n\u53bb\u9664\u91cd\u590d<\/p>\n
import java.util<\/span>.ArrayList<\/span>;<\/span>\r\nimport java.util<\/span>.List<\/span>;<\/span>\r\n\r\npublic class Main {\r\n\r\n    public static void main(String[] args) {\r\n        List<Integer> collection = new ArrayList<Integer>();<\/span>\r\n        collection.add<\/span>(14<\/span>);<\/span>\r\n        collection.add<\/span>(5<\/span>);<\/span>\r\n        collection.add<\/span>(43<\/span>);<\/span>\r\n        collection.add<\/span>(89<\/span>);<\/span>\r\n        collection.add<\/span>(64<\/span>);<\/span>\r\n        collection.add<\/span>(112<\/span>);<\/span>\r\n        collection.add<\/span>(55<\/span>);<\/span>\r\n        collection.add<\/span>(55<\/span>);<\/span>\r\n        collection.add<\/span>(58<\/span>);<\/span>\r\n        collection.stream<\/span>().distinct<\/span>().forEach<\/span>(System.out<\/span>::println);;<\/span>\r\n    }\r\n}<\/code><\/pre>\n
4\u3001Sort \u6392\u5e8f<\/strong>
\n\u6392\u5e8f\u662f\u4e00\u4e2a\u4e2d\u95f4\u64cd\u4f5c\uff0c\u8fd4\u56de\u7684\u662f\u6392\u5e8f\u597d\u540e\u7684Stream\u3002\u5982\u679c\u4f60\u4e0d\u6307\u5b9a\u4e00\u4e2a\u81ea\u5b9a\u4e49\u7684Comparator\u5219\u4f1a\u4f7f\u7528\u9ed8\u8ba4\u6392\u5e8f\u3002<\/p>\n
stringCollection\r\n    .stream<\/span>()\r\n    .sorted<\/span>()\r\n    .filter<\/span>((s) -> s.startsWith<\/span>(\"a\"<\/span>))\r\n    .forEach<\/span>(System.out<\/span>::println);<\/span>\r\n\/\/ \"aaa1\"<\/span>, \"aaa2\"<\/span><\/code><\/pre>\n
\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u6392\u5e8f\u53ea\u521b\u5efa\u4e86\u4e00\u4e2a\u6392\u5217\u597d\u540e\u7684Stream\uff0c\u800c\u4e0d\u4f1a\u5f71\u54cd\u539f\u6709\u7684\u6570\u636e\u6e90\uff0c\u6392\u5e8f\u4e4b\u540e\u539f\u6570\u636estringCollection\u662f\u4e0d\u4f1a\u88ab\u4fee\u6539\u7684\uff1a<\/p>\n
System.out<\/span>.println(stringCollection);\r\n\/\/ ddd2, aaa2, bbb1, aaa1, bbb3, ccc, bbb2, ddd1<\/span><\/code><\/pre>\n
5\u3001Map \u6620\u5c04<\/strong><\/p>\n
\u5bf9\u4e8eStream\u4e2d\u5305\u542b\u7684\u5143\u7d20\u4f7f\u7528\u7ed9\u5b9a\u7684\u8f6c\u6362\u51fd\u6570\u8fdb\u884c\u8f6c\u6362\u64cd\u4f5c\uff0c\u65b0\u751f\u6210\u7684Stream\u53ea\u5305\u542b\u8f6c\u6362\u751f\u6210\u7684\u5143\u7d20\u3002\u8fd9\u4e2a\u65b9\u6cd5\u6709\u4e09\u4e2a\u5bf9\u4e8e\u539f\u59cb\u7c7b\u578b\u7684\u53d8\u79cd\u65b9\u6cd5\uff0c\u5206\u522b\u662f\uff1amapToInt\uff0cmapToLong\u548cmapToDouble\u3002\u8fd9\u4e09\u4e2a\u65b9\u6cd5\u4e5f\u6bd4\u8f83\u597d\u7406\u89e3\uff0c\u6bd4\u5982mapToInt\u5c31\u662f\u628a\u539f\u59cbStream\u8f6c\u6362\u6210\u4e00\u4e2a\u65b0\u7684Stream\uff0c\u8fd9\u4e2a\u65b0\u751f\u6210\u7684Stream\u4e2d\u7684\u5143\u7d20\u90fd\u662fint\u7c7b\u578b\u3002\u4e4b\u6240\u4ee5\u4f1a\u6709\u8fd9\u6837\u4e09\u4e2a\u53d8\u79cd\u65b9\u6cd5\uff0c\u53ef\u4ee5\u514d\u9664\u81ea\u52a8\u88c5\u7bb1\/\u62c6\u7bb1\u7684\u989d\u5916\u6d88\u8017\uff1b<\/p>\n
import java.util<\/span>.ArrayList<\/span>;<\/span>\r\nimport java.util<\/span>.List<\/span>;<\/span>\r\n\r\npublic class Main {\r\n\r\n    public static void main(String[] args) {\r\n        List<String> collection = new ArrayList<String>();<\/span>\r\n        collection.add<\/span>(\"14\"<\/span>);<\/span>\r\n        collection.add<\/span>(\"5\"<\/span>);<\/span>\r\n        collection.add<\/span>(\"43\"<\/span>);<\/span>\r\n        collection.add<\/span>(\"89\"<\/span>);<\/span>\r\n        collection.add<\/span>(\"64\"<\/span>);<\/span>\r\n        collection.add<\/span>(\"112\"<\/span>);<\/span>\r\n        collection.add<\/span>(\"55\"<\/span>);<\/span>\r\n        collection.add<\/span>(\"55\"<\/span>);<\/span>\r\n        collection.add<\/span>(\"58\"<\/span>);<\/span>\r\n        \/\/\u5c06String\u8f6c\u5316\u4e3aInteger\u7c7b\u578b\r\n        collection.stream<\/span>().mapToInt<\/span>(Integer::valueOf).forEach<\/span>(System.out<\/span>::println);<\/span>\r\n        \/\/\u6216\r\n        collection.stream<\/span>().mapToInt<\/span>(a->Integer.parseInt<\/span>(a)).forEach<\/span>(System.out<\/span>::println);<\/span>\r\n    }\r\n}\r\n\r\n\u4e5f\u53ef\u4ee5\u8fd9\u6837\u7528\uff1a\r\nList<Integer> nums = Lists.newArrayList<\/span>(1<\/span>,1<\/span>,null,2<\/span>,3<\/span>,4<\/span>,null,5<\/span>,6<\/span>,7<\/span>,8<\/span>,9<\/span>,10<\/span>);<\/span>\r\nSystem.out<\/span>.println<\/span>(\u201csum is:\u201d+nums.stream<\/span>().filter<\/span>(num -> num != null).distinct<\/span>().mapToInt<\/span>(num -> num * 2<\/span>).\r\n            peek(System.out<\/span>::println).skip<\/span>(2<\/span>).limit<\/span>(4<\/span>).sum<\/span>());<\/span><\/code><\/pre>\n
7\u3001limit\uff1a<\/strong>
\n\u5bf9\u4e00\u4e2aStream\u8fdb\u884c\u622a\u65ad\u64cd\u4f5c\uff0c\u83b7\u53d6\u5176\u524dN\u4e2a\u5143\u7d20\uff0c\u5982\u679c\u539fStream\u4e2d\u5305\u542b\u7684\u5143\u7d20\u4e2a\u6570\u5c0f\u4e8eN\uff0c\u90a3\u5c31\u83b7\u53d6\u5176\u6240\u6709\u7684\u5143\u7d20\uff1b<\/p>\n
8\u3001skip\uff1a<\/strong>
\n\u8fd4\u56de\u4e00\u4e2a\u4e22\u5f03\u539fStream\u7684\u524dN\u4e2a\u5143\u7d20\u540e\u5269\u4e0b\u5143\u7d20\u7ec4\u6210\u7684\u65b0Stream\uff0c\u5982\u679c\u539fStream\u4e2d\u5305\u542b\u7684\u5143\u7d20\u4e2a\u6570\u5c0f\u4e8eN\uff0c\u90a3\u4e48\u8fd4\u56de\u7a7aStream\uff1b<\/p>\n
9\u3001Match \u5339\u914d<\/strong>
\nStream\u63d0\u4f9b\u4e86\u591a\u79cd\u5339\u914d\u64cd\u4f5c\uff0c\u5141\u8bb8\u68c0\u6d4b\u6307\u5b9a\u7684Predicate\u662f\u5426\u5339\u914d\u6574\u4e2aStream\u3002\u6240\u6709\u7684\u5339\u914d\u64cd\u4f5c\u90fd\u662f\u6700\u7ec8\u64cd\u4f5c\uff0c\u5e76\u8fd4\u56de\u4e00\u4e2aboolean\u7c7b\u578b\u7684\u503c\u3002<\/p>\n
boolean anyStartsWithA = \r\n    stringCollection\r\n        .stream()\r\n        .anyMatch((s) -> s.startsWith(\"a\"<\/span>))<\/span>;\r\nSystem<\/span>.out<\/span>.println<\/span>(anyStartsWithA)<\/span>;      \/\/ true<\/span>\r\nboolean<\/span> allStartsWithA<\/span> = \r\n    stringCollection<\/span>\r\n        .stream<\/span>()<\/span>\r\n        .allMatch<\/span>((s) -> s.startsWith(\"a\"<\/span>))<\/span>;\r\nSystem<\/span>.out<\/span>.println<\/span>(allStartsWithA)<\/span>;      \/\/ false<\/span>\r\nboolean<\/span> noneStartsWithZ<\/span> = \r\n    stringCollection<\/span>\r\n        .stream<\/span>()<\/span>\r\n        .noneMatch<\/span>((s) -> s.startsWith(\"z\"<\/span>))<\/span>;\r\nSystem<\/span>.out<\/span>.println<\/span>(noneStartsWithZ)<\/span>;      \/\/ true<\/span><\/span><\/code><\/pre>\n
10\u3001Count \u8ba1\u6570<\/strong><\/p>\n
\u8ba1\u6570\u662f\u4e00\u4e2a\u6700\u7ec8\u64cd\u4f5c\uff0c\u8fd4\u56deStream\u4e2d\u5143\u7d20\u7684\u4e2a\u6570\uff0c\u8fd4\u56de\u503c\u7c7b\u578b\u662flong\u3002<\/p>\n
long startsWithB = \r\n    stringCollection\r\n        .stream()\r\n        .filter((s) -> s.startsWith(\"b\"<\/span>))<\/span>\r\n        .count<\/span>()<\/span>;\r\nSystem<\/span>.out<\/span>.println<\/span>(startsWithB)<\/span>;    \/\/ 3<\/span><\/code><\/pre>\n
11\u3001Reduce \u89c4\u7ea6<\/strong>
\n\u8fd9\u662f\u4e00\u4e2a\u6700\u7ec8\u64cd\u4f5c\uff0c\u5141\u8bb8\u901a\u8fc7\u6307\u5b9a\u7684\u51fd\u6570\u6765\u8bb2stream\u4e2d\u7684\u591a\u4e2a\u5143\u7d20\u89c4\u7ea6\u4e3a\u4e00\u4e2a\u5143\u7d20\uff0c\u89c4\u8d8a\u540e\u7684\u7ed3\u679c\u662f\u901a\u8fc7Optional\u63a5\u53e3\u8868\u793a\u7684\uff1a<\/p>\n
Optional<String> reduced =\r\n    stringCollection\r\n        .stream<\/span>()\r\n        .sorted<\/span>()\r\n        .reduce<\/span>((s1, s2) -> s1 + \"#\"<\/span> + s2);<\/span>\r\nreduced.ifPresent<\/span>(System.out<\/span>::println);<\/span>\r\n\/\/ \"aaa1#aaa2#bbb1#bbb2#bbb3#ccc#ddd1#ddd2\"<\/span><\/code><\/pre>\n
Map<\/strong>
\n\u524d\u9762\u63d0\u5230\u8fc7\uff0cMap\u7c7b\u578b\u4e0d\u652f\u6301stream\uff0c\u4e0d\u8fc7Map\u63d0\u4f9b\u4e86\u4e00\u4e9b\u65b0\u7684\u6709\u7528\u7684\u65b9\u6cd5\u6765\u5904\u7406\u4e00\u4e9b\u65e5\u5e38\u4efb\u52a1\u3002<\/p>\n
Map<\/span><<\/span>Integer<\/span>, String<\/span>><\/span> map<\/span> =<\/span> new<\/span> HashMap<><\/span>();\r\nfor (int i =<\/span> 0<\/span>; i <<\/span> 10<\/span>; i++<\/span>) {\r\n    map<\/span>.<\/span>putIfAbsent(i, \"val\"<\/span> +<\/span> i);\r\n}\r\nmap<\/span>.<\/span>forEach((id, val) -> <\/span>System.<\/span>out.<\/span>println(val));<\/code><\/pre>\n
\u4ee5\u4e0a\u4ee3\u7801\u5f88\u5bb9\u6613\u7406\u89e3\uff0c putIfAbsent \u4e0d\u9700\u8981\u6211\u4eec\u505a\u989d\u5916\u7684\u5b58\u5728\u6027\u68c0\u67e5\uff0c\u800cforEach\u5219\u63a5\u6536\u4e00\u4e2aConsumer\u63a5\u53e3\u6765\u5bf9map\u91cc\u7684\u6bcf\u4e00\u4e2a\u952e\u503c\u5bf9\u8fdb\u884c\u64cd\u4f5c\u3002
\n\u4e0b\u9762\u7684\u4f8b\u5b50\u5c55\u793a\u4e86map\u4e0a\u7684\u5176\u4ed6\u6709\u7528\u7684\u51fd\u6570\uff1a<\/p>\n
map.computeIfPresent(3<\/span>, (num, val) -> val + num)<\/span>;\r\nmap<\/span>.get<\/span>(3<\/span>)<\/span>;             \/\/ val33<\/span>\r\nmap<\/span>.computeIfPresent<\/span>(9<\/span>, (num, val) -> null<\/span>)<\/span>;\r\nmap<\/span>.containsKey<\/span>(9<\/span>)<\/span>;     \/\/ false<\/span>\r\nmap<\/span>.computeIfAbsent<\/span>(23<\/span>, num -> \"val\"<\/span> + num)<\/span>;\r\nmap<\/span>.containsKey<\/span>(23<\/span>)<\/span>;    \/\/ true<\/span>\r\nmap<\/span>.computeIfAbsent<\/span>(3<\/span>, num -> \"bam\"<\/span>)<\/span>;\r\nmap<\/span>.get<\/span>(3<\/span>)<\/span>;             \/\/ val33<\/span><\/span><\/code><\/pre>\n
\u63a5\u4e0b\u6765\u5c55\u793a\u5982\u4f55\u5728Map\u91cc\u5220\u9664\u4e00\u4e2a\u952e\u503c\u5168\u90fd\u5339\u914d\u7684\u9879\uff1a<\/p>\n
map<\/span>.<\/span>remove(3<\/span>, \"val3\"<\/span>);\r\nmap<\/span>.<\/span>get(3<\/span>);             \/\/ val33<\/span>\r\nmap<\/span>.<\/span>remove(3<\/span>, \"val33\"<\/span>);\r\nmap<\/span>.<\/span>get(3<\/span>);             \/\/ null<\/span><\/code><\/pre>\n
\u53e6\u5916\u4e00\u4e2a\u6709\u7528\u7684\u65b9\u6cd5\uff1a<\/p>\n
map.getOrDefault(42<\/span>, \"not found\"<\/span>);  \/\/<\/span> not<\/span> found<\/code><\/pre>\n
\u5bf9Map\u7684\u5143\u7d20\u505a\u5408\u5e76\u4e5f\u53d8\u5f97\u5f88\u5bb9\u6613\u4e86\uff1a<\/p>\n
map.merge(9<\/span>, \"val9\"<\/span>, (value, newValue) -> value.concat(newValue))<\/span>;\r\nmap<\/span>.get<\/span>(9<\/span>)<\/span>;             \/\/ val9<\/span>\r\nmap<\/span>.merge<\/span>(9<\/span>, \"concat\"<\/span>, (value, newValue) -> value.concat(newValue))<\/span>;\r\nmap<\/span>.get<\/span>(9<\/span>)<\/span>;             \/\/ val9concat<\/span><\/span><\/code><\/pre>\n
Merge\u505a\u7684\u4e8b\u60c5\u662f\u5982\u679c\u952e\u540d\u4e0d\u5b58\u5728\u5219\u63d2\u5165\uff0c\u5426\u5219\u5219\u5bf9\u539f\u952e\u5bf9\u5e94\u7684\u503c\u505a\u5408\u5e76\u64cd\u4f5c\u5e76\u91cd\u65b0\u63d2\u5165\u5230map\u4e2d\u3002<\/p>\n
steam\u5728\u5b9e\u9645\u9879\u76ee\u4e2d\u4f7f\u7528\u7684\u4ee3\u7801\u7247\u6bb5\uff1a<\/strong><\/p>\n
\/\/<\/span>1<\/span>\u3001\u6709list\u96c6\u5408\u751f\u6210\u4ee5productId\u4e3akey\u503c\u5f97map\u96c6\u5408\r\nMap<String, List<CartManager>> cartManagerGroup =\r\n        carts.stream().collect(\r\n                Collectors.groupingBy(CartManager<\/span>::getProductId)\r\n        );\r\n\/\/<\/span>2<\/span>\u3001\u53d6\u5f97\u8d2d\u7269\u8f66\u4e2d\u6570\u91cf\u4e4b\u548c\r\nIntStream  is<\/span> = list.stream()<\/span>.mapToInt<\/span>((CartManager c)->c.getQuantity())<\/span>; \r\nis<\/span>.sum<\/span>()<\/span>;\/\/\u6570\u91cf\u4e4b\u548c\r\n\r\n\/\/3\u3001\u6240\u6709\u8ba2\u5355\u4e2d\u5546\u54c1\u6570\u91cf*\u8ba2\u5355\u91d1\u989d\u6c42\u548c\r\norderDetailsNew<\/span>.parallelStream<\/span>()<\/span>\r\n                            .mapToDouble<\/span>(orderDetailMid -> orderDetailMid.getQuantity()*orderDetailMid.getFinalPrice())<\/span>.sum<\/span>()<\/span>\r\n\r\n\/\/4\u3001\u8fc7\u6ee4\u51fa\u6307\u5b9a\u7c7b\u578b\u7684\u8ba2\u5355\uff0c\u5e76\u751f\u6210\u65b0\u7684\u96c6\u5408\r\norderDetails<\/span>.stream<\/span>()<\/span>.\r\n    filter<\/span>(orderDetail ->    StringUtil.isEmpty(orderDetail.getPromotionsType())|| !orderDetail.getPromotionsType().equals(PromotionTypeEnum.ORDERGIFTPROMOTION.getType()))<\/span>.collect<\/span>(Collectors.toList())<\/span>;\r\n\r\n\/\/5\u3001\u8fc7\u6ee4\u8d2d\u7269\u8f66\u672a\u88ab\u9009\u4e2d\u5546\u54c1\u5e76\u751f\u6210\u65b0\u7684list<\/span>\r\ncarts<\/span>.stream<\/span>()<\/span>.filter<\/span>(cart -> cart.getSelectFlag()==1<\/span>)<\/span>.collect<\/span>(Collectors.toList())<\/span>;\r\n\r\n\/\/6\u3001\u5c06list<\/span>\u4ee5\u5546\u54c1\u4fc3\u9500\u59d4key<\/span>\u8f6c\u5316\u4e3amap<\/span>\r\nMap<\/span><String<\/span>,List<\/span><PromotionsGiftProduct<\/span>>> map<\/span> = \r\n                promotionsGiftProducts<\/span>.stream<\/span>()<\/span>.collect<\/span>(                    Collectors.groupingBy(PromotionsGiftProduct::getPromotionId))<\/span>;\r\n\r\n\/\/7\u3001\u4ecelist<\/span><Cart<\/span>>\u4e2d\u5206\u79bb\u51fa\u53ea\u5b58\u50a8productId<\/span>\u7684\u5217\u8868list<\/span><String<\/span>>\r\nList<\/span><String<\/span>> productIds<\/span> = needUpdate<\/span>.parallelStream<\/span>()<\/span>\r\n                        .map<\/span>(CartManager::getProductId)<\/span>\r\n                        .collect<\/span>(Collectors.toList())<\/span>;<\/span><\/code><\/pre>\n
<\/a>\u4e5d\u3001Date API<\/h2>\n
Java 8 \u5728\u5305java.time\u4e0b\u5305\u542b\u4e86\u4e00\u7ec4\u5168\u65b0\u7684\u65f6\u95f4\u65e5\u671fAPI\u3002
\nClock \u65f6\u949f<\/strong>
\nClock\u7c7b\u63d0\u4f9b\u4e86\u8bbf\u95ee\u5f53\u524d\u65e5\u671f\u548c\u65f6\u95f4\u7684\u65b9\u6cd5\uff0cClock\u662f\u65f6\u533a\u654f\u611f\u7684\uff0c\u53ef\u4ee5\u7528\u6765\u53d6\u4ee3 System.currentTimeMillis() \u6765\u83b7\u53d6\u5f53\u524d\u7684\u5fae\u79d2\u6570\u3002\u67d0\u4e00\u4e2a\u7279\u5b9a\u7684\u65f6\u95f4\u70b9\u4e5f\u53ef\u4ee5\u4f7f\u7528Instant\u7c7b\u6765\u8868\u793a\uff0cInstant\u7c7b\u4e5f\u53ef\u4ee5\u7528\u6765\u521b\u5efa\u8001\u7684java.util.Date\u5bf9\u8c61\u3002<\/p>\n
Clock<\/span> clock = Clock<\/span>.systemDefaultZone();\r\nlong millis = clock.millis();\r\nInstant instant = clock.instant();\r\nDate<\/span> legacyDate = Date<\/span>.from(instant);   \/\/ legacy java.util.Date<\/span><\/code><\/pre>\n
Timezones \u65f6\u533a<\/strong><\/p>\n
System.out<\/span>.println<\/span>(ZoneId.getAvailableZoneIds<\/span>());<\/span>\r\n\/\/ prints all available timezone ids\r\nZoneId zone1 = ZoneId.of<\/span>(\"Europe\/Berlin\"<\/span>);<\/span>\r\nZoneId zone2 = ZoneId.of<\/span>(\"Brazil\/East\"<\/span>);<\/span>\r\nSystem.out<\/span>.println<\/span>(zone1.getRules<\/span>());<\/span>\r\nSystem.out<\/span>.println<\/span>(zone2.getRules<\/span>());<\/span>\r\n\/\/ ZoneRules[currentStandardOffset=+01<\/span>:00<\/span>]\r\n\/\/ ZoneRules[currentStandardOffset=-03<\/span>:00<\/span>]<\/code><\/pre>\n
LocalTime \u672c\u5730\u65f6\u95f4<\/strong>
\nLocalTime \u5b9a\u4e49\u4e86\u4e00\u4e2a\u6ca1\u6709\u65f6\u533a\u4fe1\u606f\u7684\u65f6\u95f4\uff0c\u4f8b\u5982 \u665a\u4e0a10\u70b9\uff0c\u6216\u8005 17:30:15\u3002\u4e0b\u9762\u7684\u4f8b\u5b50\u4f7f\u7528\u524d\u9762\u4ee3\u7801\u521b\u5efa\u7684\u65f6\u533a\u521b\u5efa\u4e86\u4e24\u4e2a\u672c\u5730\u65f6\u95f4\u3002\u4e4b\u540e\u6bd4\u8f83\u65f6\u95f4\u5e76\u4ee5\u5c0f\u65f6\u548c\u5206\u949f\u4e3a\u5355\u4f4d\u8ba1\u7b97\u4e24\u4e2a\u65f6\u95f4\u7684\u65f6\u95f4\u5dee\uff1a<\/p>\n
LocalTime now1 = LocalTime.now<\/span>(zone1);<\/span>\r\nLocalTime now2 = LocalTime.now<\/span>(zone2);<\/span>\r\nSystem.out<\/span>.println<\/span>(now1.isBefore<\/span>(now2));  \/\/ false<\/span>\r\nlong hoursBetween = ChronoUnit.HOURS<\/span>.between<\/span>(now1, now2);<\/span>\r\nlong minutesBetween = ChronoUnit.MINUTES<\/span>.between<\/span>(now1, now2);<\/span>\r\nSystem.out<\/span>.println<\/span>(hoursBetween);       \/\/ -3<\/span>\r\nSystem.out<\/span>.println<\/span>(minutesBetween);     \/\/ -239<\/span><\/code><\/pre>\n
LocalTime \u63d0\u4f9b\u4e86\u591a\u79cd\u5de5\u5382\u65b9\u6cd5\u6765\u7b80\u5316\u5bf9\u8c61\u7684\u521b\u5efa\uff0c\u5305\u62ec\u89e3\u6790\u65f6\u95f4\u5b57\u7b26\u4e32\u3002<\/p>\n
LocalTime late = LocalTime.of<\/span>(23<\/span>, 59<\/span>, 59<\/span>);<\/span>\r\nSystem.out<\/span>.println<\/span>(late);       \/\/ 23:59:59<\/span>\r\nDateTimeFormatter germanFormatter =\r\n    DateTimeFormatter\r\n        .ofLocalizedTime<\/span>(FormatStyle.SHORT<\/span>)\r\n        .withLocale<\/span>(Locale.GERMAN<\/span>);<\/span>\r\nLocalTime leetTime = LocalTime.parse<\/span>(\"13:37\"<\/span>, germanFormatter);<\/span>\r\nSystem.out<\/span>.println<\/span>(leetTime);   \/\/ 13:37<\/span><\/code><\/pre>\n
LocalDate \u672c\u5730\u65e5\u671f<\/strong>
\nLocalDate \u8868\u793a\u4e86\u4e00\u4e2a\u786e\u5207\u7684\u65e5\u671f\uff0c\u6bd4\u5982 2014-03-11\u3002\u8be5\u5bf9\u8c61\u503c\u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u7528\u8d77\u6765\u548cLocalTime\u57fa\u672c\u4e00\u81f4\u3002\u4e0b\u9762\u7684\u4f8b\u5b50\u5c55\u793a\u4e86\u5982\u4f55\u7ed9Date\u5bf9\u8c61\u52a0\u51cf\u5929\/\u6708\/\u5e74\u3002\u53e6\u5916\u8981\u6ce8\u610f\u7684\u662f\u8fd9\u4e9b\u5bf9\u8c61\u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u64cd\u4f5c\u8fd4\u56de\u7684\u603b\u662f\u4e00\u4e2a\u65b0\u5b9e\u4f8b\u3002<\/p>\n
LocalDate today = LocalDate.now<\/span>();<\/span>\r\nLocalDate tomorrow = today.plus<\/span>(1<\/span>, ChronoUnit.DAYS<\/span>);<\/span>\r\nLocalDate yesterday = tomorrow.minusDays<\/span>(2<\/span>);<\/span>\r\nLocalDate independenceDay = LocalDate.of<\/span>(2014<\/span>, Month.JULY<\/span>, 4<\/span>);<\/span>\r\nDayOfWeek dayOfWeek = independenceDay.getDayOfWeek<\/span>();<\/span>\r\n\r\nSystem.out<\/span>.println<\/span>(dayOfWeek);    \/\/ FRIDAY<\/span><\/code><\/pre>\n
\u4ece\u5b57\u7b26\u4e32\u89e3\u6790\u4e00\u4e2aLocalDate\u7c7b\u578b\u548c\u89e3\u6790LocalTime\u4e00\u6837\u7b80\u5355\uff1a<\/p>\n
DateTimeFormatter germanFormatter =\r\n    DateTimeFormatter\r\n        .ofLocalizedDate<\/span>(FormatStyle.MEDIUM<\/span>)\r\n        .withLocale<\/span>(Locale.GERMAN<\/span>);<\/span>\r\nLocalDate xmas = LocalDate.parse<\/span>(\"24.12.2014\"<\/span>, germanFormatter);<\/span>\r\nSystem.out<\/span>.println<\/span>(xmas);   \/\/ 2014-12-24<\/span><\/code><\/pre>\n
LocalDateTime \u672c\u5730\u65e5\u671f\u65f6\u95f4
\nLocalDateTime \u540c\u65f6\u8868\u793a\u4e86\u65f6\u95f4\u548c\u65e5\u671f\uff0c\u76f8\u5f53\u4e8e\u524d\u4e24\u8282\u5185\u5bb9\u5408\u5e76\u5230\u4e00\u4e2a\u5bf9\u8c61\u4e0a\u4e86\u3002LocalDateTime\u548cLocalTime\u8fd8\u6709LocalDate\u4e00\u6837\uff0c\u90fd\u662f\u4e0d\u53ef\u53d8\u7684\u3002LocalDateTime\u63d0\u4f9b\u4e86\u4e00\u4e9b\u80fd\u8bbf\u95ee\u5177\u4f53\u5b57\u6bb5\u7684\u65b9\u6cd5\u3002<\/p>\n
LocalDateTime sylvester = LocalDateTime.of<\/span>(2014<\/span>, Month.DECEMBER<\/span>, 31<\/span>, 23<\/span>, 59<\/span>, 59<\/span>);<\/span>\r\nDayOfWeek dayOfWeek = sylvester.getDayOfWeek<\/span>();<\/span>\r\nSystem.out<\/span>.println<\/span>(dayOfWeek);      \/\/ WEDNESDAY<\/span>\r\nMonth month = sylvester.getMonth<\/span>();<\/span>\r\nSystem.out<\/span>.println<\/span>(month);          \/\/ DECEMBER<\/span>\r\nlong minuteOfDay = sylvester.getLong<\/span>(ChronoField.MINUTE<\/span>_OF_DAY);<\/span>\r\nSystem.out<\/span>.println<\/span>(minuteOfDay);    \/\/ 1439<\/span><\/code><\/pre>\n
\u53ea\u8981\u9644\u52a0\u4e0a\u65f6\u533a\u4fe1\u606f\uff0c\u5c31\u53ef\u4ee5\u5c06\u5176\u8f6c\u6362\u4e3a\u4e00\u4e2a\u65f6\u95f4\u70b9Instant\u5bf9\u8c61\uff0cInstant\u65f6\u95f4\u70b9\u5bf9\u8c61\u53ef\u4ee5\u5f88\u5bb9\u6613\u7684\u8f6c\u6362\u4e3a\u8001\u5f0f\u7684java.util.Date\u3002<\/p>\n
Instant instant = sylvester\r\n        .atZone<\/span>(ZoneId.systemDefault<\/span>())\r\n        .toInstant<\/span>();<\/span>\r\nDate legacyDate = Date.from<\/span>(instant);<\/span>\r\nSystem.out<\/span>.println<\/span>(legacyDate);     \/\/ Wed Dec 31 23:59:59 CET 2014<\/span><\/code><\/pre>\n
\u683c\u5f0f\u5316LocalDateTime\u548c\u683c\u5f0f\u5316\u65f6\u95f4\u548c\u65e5\u671f\u4e00\u6837\u7684\uff0c\u9664\u4e86\u4f7f\u7528\u9884\u5b9a\u4e49\u597d\u7684\u683c\u5f0f\u5916\uff0c\u6211\u4eec\u4e5f\u53ef\u4ee5\u81ea\u5df1\u5b9a\u4e49\u683c\u5f0f\uff1a<\/p>\n
DateTimeFormatter formatter =\r\n    DateTimeFormatter\r\n        .ofPattern<\/span>(\"MMM dd, yyyy - HH:mm\"<\/span>);<\/span>\r\nLocalDateTime parsed = LocalDateTime.parse<\/span>(\"Nov 03, 2014 - 07:13\"<\/span>, formatter);<\/span>\r\nString string = formatter.format<\/span>(parsed);<\/span>\r\nSystem.out<\/span>.println<\/span>(string);     \/\/ Nov 03, 2014 - 07:13<\/span><\/code><\/pre>\n
\u548cjava.text.NumberFormat\u4e0d\u4e00\u6837\u7684\u662f\u65b0\u7248\u7684DateTimeFormatter\u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u6240\u4ee5\u5b83\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\u3002
\n\u5173\u4e8e\u65f6\u95f4\u65e5\u671f\u683c\u5f0f\u7684\u8be6\u7ec6\u4fe1\u606f\uff1a
\nhttp:\/\/download.java.net\/jdk8\/docs\/api\/java\/time\/format\/DateTimeFormatter.html<\/a><\/p>\n
<\/a>\u5341\u3001Annotation \u6ce8\u89e3<\/h2>\n
\u5728Java 8\u4e2d\u652f\u6301\u591a\u91cd\u6ce8\u89e3\u4e86<\/p>\n
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\u8f6c\u8f7d\u8bf7\u6ce8\u660e\uff1a\u5de6\u624b\u4ee3\u7801\u53f3\u624b\u8bd7<\/a> » JDK8 \u5341\u5927\u65b0\u7279\u6027<\/a><\/p>
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