java比较器Comparable和Comparator的使用

向右看齐 2022-08-11 16:46 234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;
            }
        }
        
    }