语法 ()->{}

Lambda表达式不是替代匿名内部类，因为编译后没有生成内部类的class文件。

1，多线程示例：

java8以前的多线程写法

package com.wjb.lambda;
/**
 * Created by ptdy on 2017/5/17.
 */
public class ThreadDemo1 implements Runnable{
    @Override
    public void run() {
        for(int i = 0;i<100;i++){
            System.out.println("run:"+i);
        }
    }
    public static void main(String[] args) {
        Thread thread = new Thread(new ThreadDemo1());
        thread.start();
        for(int i = 0;i<100;i++){
            System.out.println("main:"+i);
        }
    }
}

java8以前匿名内部类的写法

package com.wjb.lambda;
/**
 * Created by ptdy on 2017/5/17.
 */
public class ThreadDemo2 {
    public static void main(String[] args) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                for(int i = 0;i < 100;i++){
                    System.out.println("run:"+i);
                }
            }
        }).start();
        for(int x = 0;x<100;x++){
            System.out.println("main:"+x);
        }
    }
}

java8的Lambda表达式写法

package com.wjb.lambda;
/**
 * Created by ptdy on 2017/5/17.
 */
public class ThreadDemo3 {
    public static void main(String[] args) {
        Runnable runnable = ()->{
            for(int i = 0;i < 100;i++){
                System.out.println("run..."+i);
            }
        };
        new Thread(runnable).start();
        for (int i = 0;i < 100;i ++){
            System.out.println("main..."+i);
        }
    }
}

2，TreeSet排序示例

java8以前的写法

package com.wjb.lambda;

import java.util.Comparator;
import java.util.TreeSet;

/**
 * Created by ptdy on 2017/5/17.
 */
public class TreeSetLambda1 {
    public static void main(String[] args) {
        TreeSet treeSet = new TreeSet(new StringLength());
        treeSet.add("a");
        treeSet.add("eb");
        treeSet.add("vbc");
        treeSet.add("badsds");
        System.out.println(treeSet);

    }
    static class StringLength implements Comparator<String>{
        @Override
        public int compare(String o1, String o2) {
            int length = o1.length() - o2.length();
            return length == 0 ? o1.compareTo(o2):length;
        }
    }
}

java8以前的匿名内部类写法

package com.wjb.lambda;

import java.util.Comparator;
import java.util.TreeSet;

/**
 * Created by ptdy on 2017/5/17.
 */
public class TreeSetLambda2 {
    public static void main(String[] args) {
        TreeSet treeSet = new TreeSet(new Comparator<String>() {
            @Override
            public int compare(String o1, String o2) {
                int length = o1.length() - o2.length();
                return length == 0 ? o1.compareTo(o2):length;
            }
        });
        treeSet.add("a");
        treeSet.add("eb");
        treeSet.add("vbc");
        treeSet.add("badsds");
        System.out.println(treeSet);
    }
}

java8的Lambda写法

package com.wjb.lambda;
import java.util.Set;
import java.util.TreeSet;

/**
 * Created by ptdy on 2017/5/17.
 */
public class TreeSetLambda3 {
    public static void main(String[] args) {
        Set<String> treeSet = new TreeSet<String>((s1, s2)->{
            int length = s1.length() - s2.length();
            return length == 0 ? s1.compareTo(s2):length;
        });
        treeSet.add("a");
        treeSet.add("eb");
        treeSet.add("vbc");
        treeSet.add("badsds");
        System.out.println(treeSet);
    }
}

3,F盘文件名过滤

java8以前写法

package com.wjb.lambda;

import java.io.File;
import java.io.FileFilter;

/**
 * Created by ptdy on 2017/5/17. 
 */
public class FileLambda1 {
    public static class FileTxt implements FileFilter{
        @Override
        public boolean accept(File pathname) {
            return pathname.getName().endsWith(".txt");
        }
    }
    public static void main(String[] args) {
        File file = new File("F:\\demo");
        File[] files = file.listFiles(new FileTxt());   //获取demo目录下的所有文件名
        for (File f:files){
            System.out.println(f);
        }
    }
}

java8的Lambda写法

package com.wjb.lambda;

import java.io.File;

/**
 * Created by ptdy on 2017/5/17.
 */
public class FileLambda1 {
    public static void main(String[] args) {
        File file = new File("F:\\demo");
        File[] files = file.listFiles((pathname)->{
            return pathname.getName().endsWith(".txt");
        });
        for (File f:files){
            System.out.println(f);
        }
    }
}