lambda表达式推导和使用

Posted 2022-05-08 116970u

lambda

• λ希腊字母表中排序第十一位的字母，英语名称为 Lambda，
• 避免匿名内部类定义过多
• 其实质属于函数式编程的概念

(params) -> expression  
(params) -> statement  
(params) ->  statements 

new Thread(()->System.out.println("多线程学习。。。")).start();

1、lambda表达式逐级推导

 1 package com.sxt.thread;
 2 
 3 /**
 4  * Lambda表达式 简化线程（用一次）的使用
 5  */
 6 public class LambdaThread 
 7 
 8     //静态内部类
 9     static class Test implements Runnable 
10         public void run() 
11             for (int i = 0; i < 20; i++) 
12                 System.out.println("一边听歌");
13             
14         
15     
16 
17     public static void main(String[] args) 
18 
19         //new Thread(new Test()).start();
20 
21         //局部内部类
22         class Test2 implements Runnable 
23             public void run() 
24                 for (int i = 0; i < 20; i++) 
25                     System.out.println("一边听歌");
26                 
27             
28         
29 
30         new Thread(new Test2()).start();
31 
32         //匿名内部类 必须借助接口或是父类
33         new Thread(new Runnable() 
34             @Override
35             public void run() 
36                 for (int i = 0; i < 20; i++) 
37                     System.out.println("一边听歌");
38                 
39             
40         ).start();
41 
42         //jdk8简化
43         new Thread(() -> 
44             for (int i = 0; i < 20; i++) 
45                 System.out.println("一边听歌");
46             
47         ).start();
48     
49 

2、再次推导，加深印象

 1 package com.sxt.thread;
 2 
 3 /**
 4  * @ClassName LambdaTest01
 5  * @Description TODO
 6  * @Date 2019/7/23 22:46
 7  * @Version 1.0
 8  */
 9 public class LambdaTest01 
10 
11     //静态内部类
12     static class Like2 implements ILike
13 
14         @Override
15         public void lambda() 
16             System.out.println("I Like Lambda2");
17         
18     
19 
20     public static void main(String[] args) 
21 
22         ILike like = new Like();
23         like.lambda();
24 
25         like = new Like2();
26         like.lambda();
27 
28         //方法内部类
29         class Like3 implements ILike
30 
31             @Override
32             public void lambda() 
33                 System.out.println("I Like Lambda3");
34             
35         
36         like = new Like3();
37         like.lambda();
38 
39         //匿名内部类
40         like = new ILike() 
41             @Override
42             public void lambda() 
43                 System.out.println("I Like Lambda4");
44             
45         ;
46         like.lambda();
47         //lambda推导必须存在类型
48         like = () -> 
49             System.out.println("I Like Lambda5");
50         ;
51         like.lambda();
52     
53 
54 
55 interface ILike
56     void lambda();
57 
58 
59 //外部类
60 class Like implements ILike
61 
62     @Override
63     public void lambda() 
64         System.out.println("I Like Lambda");
65     
66 

3、lambda参数传递（无返回值）以及简化

 1 package com.sxt.thread;
 2 
 3 /**
 4  * lambda推导+参数
 5  */
 6 public class LambdaTest02 
 7 
 8 
 9     public static void main(String[] args) 
10         ILove love = (int a) -> 
11             System.out.println("I Like Lambda-->" + a);
12         ;
13         love.lambda(100);
14 
15         //简化
16         love = (a) -> 
17             System.out.println("I Like Lambda-->" + a);
18         ;
19         love.lambda(60);
20 
21         //只有一个参数，（）可以省略
22         love = a -> 
23             System.out.println("I Like Lambda-->" + a);
24         ;
25         love.lambda(80);
26 
27         //如果代码只是一行，还可以省略
28         love = a -> System.out.println("I Like Lambda-->" + a);
29         love.lambda(90);
30     
31 
32 
33 interface ILove 
34     void lambda(int a);
35 
36 
37 //外部类
38 class Love implements ILove 
39 
40     @Override
41     public void lambda(int a) 
42         System.out.println("I Like Lambda-->" + a);
43     
44 

4、多个参数+返回值

 1 package com.sxt.thread;
 2 
 3 /**
 4  * lambda推导+参数+返回值
 5  */
 6 public class LambdaTest03 
 7 
 8 
 9     public static void main(String[] args) 
10         IInterest interest = (int a, int c)-> 
11             System.out.println("I Like Lambda-->" + (a + c));
12             return a + c;
13         ;
14 
15         interest.lambda(100,200);
16 
17         interest = (a,c)-> 
18             System.out.println("I Like Lambda-->" + (a + c));
19             return a + c;
20         ;
21         interest.lambda(200,200);
22 
23         //()不可以省略
24         /*interest = a,c-> 
25             System.out.println("I Like Lambda-->" + (a + c));
26             return a + c;
27         ;*/
28 
29         interest = (a,c)-> 
30             return a + c;
31         ;
32 
33         interest = (a,c)->a+c;
34 
35         interest = (a,c)->100;
36 
37 
38         System.out.println(interest.lambda(10,20));
39 
40 
41     
42 
43 
44 
45 interface IInterest 
46     int lambda(int a, int b);
47 
48 
49 //外部类
50 class Interest implements IInterest 
51 
52     @Override
53     public int lambda(int a, int c) 
54         System.out.println("I Like Lambda-->" + (a + c));
55         return a + c;
56     
57 

5、多线程示例

 1 package com.sxt.thread;
 2 
 3 /**
 4  * lambda推导+参数+返回值
 5  */
 6 public class LambdaTest04 
 7 
 8     public static void main(String[] args) 
 9 
10         new Thread(()->
11             for (int i = 0; i <100 ; i++) 
12                 System.out.println("123");
13             
14         ).start();
15 
16         new Thread(()->System.out.println("456")).start();
17     
18 
19