Java中lambda表达式的基本运用

刺骨的言语ヽ痛彻心扉 2023-10-01 16:29 7阅读 0赞

### 一、实现接口 ###

调用一个接口中的方法，传统方法：  
接口类A：

package lombda;
    
    /**
     * @author yeqv
     * @program A2
     * @Classname A
     * @Date 2022/1/25 20:38
     * @Email w16638771062@163.com
     */
    public interface A {
        
        int po(int i);
        
    }

实现接口：

package lombda;
    
    /**
     * @author yeqv
     * @program A2
     * @Classname B
     * @Date 2022/1/25 20:43
     * @Email w16638771062@163.com
     */
    public class B implements A {
        
        public int po(int i) {
        
            return i * i;
        }
    }

调用接口中的方法po()

package lombda;
    
    /**
     * @author yeqv
     * @program A2
     * @Classname LB1
     * @Date 2022/1/25 20:35
     * @Email w16638771062@163.com
     */
    public class LB1 {
        
        public static void main(String[] args) {
        
            A ab = new B();
            System.out.println(ab.po(5));
        }
    
    }

![在这里插入图片描述][8a6d7b901c944620b56caa260933c104.png]  
运用lambda表达式后的代码可以直接调用接口A中的方法，不用再创建个类实现接口。

package lombda;
    
    /**
     * @author yeqv
     * @program A2
     * @Classname LB1
     * @Date 2022/1/25 20:35
     * @Email w16638771062@163.com
     */
    public class LB1 {
        
        public static void main(String[] args) {
        
            var ab = (A) x -> x * x;
            System.out.println(ab.po(5));
        }
    
    }

### 二、数字排序 ###

![在这里插入图片描述][12d3b8cd3a234f61aa6507d800728137.png]

### 三、字符串排序方法 ###

package lombda;
    
    import java.util.Arrays;
    import java.util.Random;
    
    /**
     * @author yeqv
     * @program A2
     * @Classname LB1
     * @Date 2022/1/25 20:35
     * @Email w16638771062@163.com
     */
    public class LB1 {
        
        public static void main(String[] args) {
        
        /*    //定义数组
            Integer[] integers = new Integer[]{1, 23, 6, 8, 2, 3};
            System.out.println(Arrays.toString(integers));
            //正序排序
            Arrays.sort(integers);
            System.out.println(Arrays.toString(integers));
            //逆序排序
            Arrays.sort(integers, (a, b) -> b - a);
            System.out.println(Arrays.toString(integers));
            //乱序排序
            Random random = new Random();
            Arrays.sort(integers, (a, b) -> random.nextBoolean() ? 1 : -1);
            System.out.println(Arrays.toString(integers));*/
    //定义字符串数组
            String[] strings = new String[]{
        "asd", "rtyuj", "vgj", "bdf"};
            System.out.println(Arrays.toString(strings));
            //正序
            Arrays.sort(strings, (a, b) -> a.compareTo(b));
            System.out.println(Arrays.toString(strings));
            //逆序
            Arrays.sort(strings, (a, b) -> b.compareTo(a));
            System.out.println(Arrays.toString(strings));
            //乱序
            Random random = new Random();
            Arrays.sort(strings, (a, b) -> random.nextBoolean() ? 1 : -1);
            System.out.println(Arrays.toString(strings));
        }
    
    }

![在这里插入图片描述][0282361f2d894267a2fa2b8a52e3072a.png]

### 四、对象排序 ###

先建立个User类

package lombda;
    
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    /**
     * @author yeqv
     * @program A2
     * @Classname User
     * @Date 2022/1/25 21:26
     * @Email w16638771062@163.com
     */
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class User {
        
        private int id;
        private String name;
    
    }

再进行排序

package lombda;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /**
     * @author yeqv
     * @program A2
     * @Classname LB2
     * @Date 2022/1/25 21:27
     * @Email w16638771062@163.com
     */
    public class LB2 {
        
        public static void main(String[] args) {
        
            //定义一个集合
            List<User> list = new ArrayList<User>(List.of(new User(1, "张三"), new User(5, "张四"), new User(2, "张五"), new User(3, "张六")));
            //以user对象的id来排序
            list.sort((a, b) -> a.getId() - b.getId());
            System.out.println(list);
    
        }
    }

[8a6d7b901c944620b56caa260933c104.png]: https://img-blog.csdnimg.cn/8a6d7b901c944620b56caa260933c104.png
[12d3b8cd3a234f61aa6507d800728137.png]: https://img-blog.csdnimg.cn/12d3b8cd3a234f61aa6507d800728137.png
[0282361f2d894267a2fa2b8a52e3072a.png]: https://img-blog.csdnimg.cn/0282361f2d894267a2fa2b8a52e3072a.png