Java 源码分析-Comparator Comparable 接口

Z时代
2024-01-10
分类：综合

java

Comparable 介绍

首先类要继承 Comparable 接口，还需要实现接口定义的比较方法，在这些方法中传入需要比较大小的另一个对象，通过选定的成员变量与之比较，如果大于则返回 1，小于返回 -1，相等返回 0。

Comparable 使用示例

public class People implements Comparable<People>{    
    private String name;  
    private int age;
    public People(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    @Override
    public int compareTo(People o) {
        // 按年龄从小到大排序
        if(this.age > o.getAge()) {
            return 1;
        } else if (this.age < o.getAge()) {
            return -1;
        }
        // 相等情况
        return 0;
    }
}

排序测试：

import java.util.ArrayList;
import java.util.Collections;
public class Test {    
    public static void main(String[] args) {
        People p1 = new People("fei", 35);
        People p2 = new People("qiang", 22);
        People p3 = new People("sheng", 24);
        ArrayList<People> list = new ArrayList<People>();
        list.add(p1);
        list.add(p2);
        list.add(p3);
        Collections.sort(list);
        for(People p:list) {
            System.out.println("name:"+p.getName()+", age:"+p.getAge()+"。");
        }
    }
}
结果：
name:qiang, age:22。
name:sheng, age:24。
name:fei, age:35。

Comparator 使用示例

import java.util.Comparator;
public class PeopleComparator implements Comparator<People>{
    @Override
    public int compare(People o1, People o2) {
        // 从大到小排序
       if(o1.getAge() > o2.getAge()) {
           return -1;
       } else if (o1.getAge() < o2.getAge()) {
           return 1;
       }
        return 0;
    }
}

排序测试：

public class Test {    
    public static void main(String[] args) {
        People p1 = new People("fei", 35);
        People p2 = new People("qiang", 22);
        People p3 = new People("sheng", 24);
        ArrayList<People> list = new ArrayList<People>();
        list.add(p1);
        list.add(p2);
        list.add(p3);
        // 指定一个比较器
        list.sort(new PeopleComparator());
        for(People p:list) {
            System.out.println("name:"+p.getName()+", age:"+p.getAge()+"。");
        }
    }
}
结果：
name:fei, age:35。
name:sheng, age:24。
name:qiang, age:22。