Java中lambda表达式的基本运用

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));
    }

}

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

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));


    }

}

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));
    }

}

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);

    }
}