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运行环境

1. 安装JDK8；

   直接安装，并修改环境变量“JAVA_HOME”为相应文件夹

2. 设置eclipse的JRE为JDK8下的jre；

   “Window”->”Reference”->”Java”->”Installed JREs”->添加默认jre（注意以往的项目还是基于原默认的JRE需手动修改为当前JRE）

3. 安装“JAVA8 support for Eclipse keplerSR2”插件

   “Help”->”Eclipse Marketplace…”->输入“JAVA 8 Kelper”搜索->安装插件。

示例代码

import java.util.Arrays;import java.util.List;import java.util.function.Predicate;public class Main {
       public static void main(String []args){          List
   
     languages = Arrays.asList("Java", "Scala", "C++", "Haskela", "Lisp");          System.out.println("Languages which starts with J :");          filter(languages, (str)->((String) str).startsWith("J"));          System.out.println("Languages which ends with a ");          filter(languages, (str)->((String) str).endsWith("a"));          System.out.println("Print all languages :");          filter(languages, (str)->true);           System.out.println("Print no language : ");           filter(languages, (str)->false);           System.out.println("Print language whose length greater than 4:");           filter(languages, (str)->((String) str).length() > 4);            //注意Stream用法，            List
    
      lowercaseNames = languages.stream().map(name -> name.toLowerCase()).collect(Collectors.toList());           System.out.println("Print language in lowercase:");           for(String str:lowercaseNames)           {               System.out.println(str);           }    }     @SuppressWarnings("unchecked")//忽视IDE提示的警告    public static void filter(List
     
       names, @SuppressWarnings("rawtypes") Predicate condition) {        for(String name: names)  {           if(condition.test(name)) {              System.out.println(name + " ");           }        }      }}
     
    
   

基本语法

1. Lambda 理解：一段带有输入参数的可执行语句块。实质是一种，是声明式编程（）

   （维基百科解释：a function (or a subroutine) defined, and possibly called, without being bound to an identifier。）

2. lambda表达式的一般语法:是一种匿名方法，参考文档

//一般省略参数类型，编译器能够根据上下文自动识别参数类型//只有一个参数可以省略小括号//只有一句代码可以省略大括号//lambda访问的外部变量不可变，java的匿名内部类在访问外部变量的时候，外部变量必须用final修饰，lambda编译器隐式转换成final来处理//lambda中this是指声明它的外部对象//(Type1 param1, Type2 param2, ..., TypeN paramN) -> {  statment1;  statment2;  //.............  return statmentM;}

3.lambda的函数调用，必须基于接口。

public class Main {       interface HelloService {          String hello(String firstname, String lastname);       }       public static void main(String[] args) {    HelloService helloService=(String firstname, String lastname) ->     { String hello="Hello " + firstname + " " + lastname; return hello; };    System.out.println(helloService.hello(args[0], args[1]));                   }    }

interface WorkflowManager{    public default void doTask1(){        System.out.println("Doing Task1...");    }    public void doTask2();    public default void doTask3(){        System.out.println("Doing Task3...");    }    public default void doTask4(){        System.out.println("Doing Task4...");    }}public class Main {        public static void main(String[] args) {           /**                 * Using lambda expression to create different                  * implementation of the abstract workflow             */            initiateWorkFlow(()->System.out.println("Doing Task2.1..."));            initiateWorkFlow(()->System.out.println("Doing Task2.2..."));            initiateWorkFlow(()->System.out.println("Doing Task2.3..."));        }        static void initiateWorkFlow(WorkflowManager workflowMgr){            System.out.println("Starting the workflow ...");            workflowMgr.doTask1();            workflowMgr.doTask2();            workflowMgr.doTask3();            workflowMgr.doTask4();        }    }

参考资料：

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