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 [e-mail]
 */
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 [e-mail]
 */
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 [e-mail]
 */
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 [e-mail]
 */
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 [e-mail]
 */
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 [e-mail]
 */
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 [e-mail]
 */
@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 [e-mail]
 */
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);

    }
}

总结

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