java比较器Comparable和Comparator的使用-蒲公英云

java比较器Comparable和Comparator的使用

向右看齐 2022-08-11 16:46 294阅读 0赞

java的比较器有两类，分别是Comparable接口和Comparator接口。

在为对象数组进行排序时，比较器就有非常大的作用

1、使用comparable接口，需要重写compareTo(T o) 方法，在其中定义排序规则，那么就可以直接调用java.util.Arrays.sort()来排序对象数组，

例子：

package com.yaoxun.test;
public class Student implements Comparable<Student> {
    private int score;
    private int age;
    @Override
    public int compareTo(Student o) {
        if(this.score > o.score)
            return 1;
        else if(this.score < o.score) 
            return -1;
        else {
            if(this.age > o.age)
                return 1;
            else if(this.age < o.age) 
                return -1;
            else
                return 0;
        }
    }
}

2、使用Comparator接口，需要重写 compare(T o1, T o2) 方法，

package edu.sjtu.ist.comutil;
import java.util.Comparator;
class Student {
    private String name;
    private int age;
    private float score;
    public Student(String name, int age, float score) {
        this.name = name;
        this.age = age;
        this.score = score;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public float getScore() {
        return score;
    }
    public void setScore(float score) {
        this.score = score;
    }
    public String toString()
    {
        return name+"\t\t"+age+"\t\t"+score;
    }
}
class StudentComparator implements Comparator<Student>{
    @Override
    public int compare(Student o1, Student o2) {
        // TODO Auto-generated method stub
        if(o1.getScore()>o2.getScore())
            return -1;
        else if(o1.getScore()<o2.getScore())
            return 1;
        else{
            if(o1.getAge()>o2.getAge())
                return 1;
            else if(o1.getAge()<o2.getAge())
                return -1;
            else 
                return 0;
        }
    }
}