TreeSet集合的排序

痛定思痛。 2022-03-07 10:54 255阅读 0赞

### 一、使用Comparator比较器： ###

import java.util.Collection;
    import java.util.Comparator;
    import java.util.HashMap;
    import java.util.HashSet;
    import java.util.Iterator;
    import java.util.Map;
    import java.util.Scanner;
    import java.util.Set;
    import java.util.TreeSet;
    class Student{
        String name;
        int score;
    	public Student(String name, int score) {
    		super();
    		this.name = name;
    		this.score = score;
    	}
    	@Override
    	public String toString() {
    		// TODO Auto-generated method stub
    		return this.name+" "+this.score;
    	}
        
    }
    public class Main{
        public static void main(String[] args) {
        	Scanner cin = new Scanner(System.in);
        	Student [] s = {
        			new Student("skh",100),
        			new Student("xiaoming",98),
        			new Student("xiaohong",99),
        			new Student("azxx",100),
        			new Student("xh",99),
        			new Student("bz",100),
        			
        	};
        TreeSet <Student> set = new TreeSet<Student>(new Comparator<Student>() {
    
    		@Override
    		public int compare(Student a, Student b) {
    			int j = b.score - a.score;
    			if(j==0) {
    		return a.name.compareTo(b.name);
    			}
    			else
    				return j;
    	}
        });
        for(Student i:s) {
        	set.add(i);
        }
        for(Student i:set) {
        	System.out.println(i);
        }
       }     
    }

在这里实现按照成绩降序输出，如果成绩相同则按姓氏来排序，输出结果：

azxx 100
    bz 100
    skh 100
    xh 99
    xiaohong 99
    xiaoming 98

### 二、使用Comparable接口方式来排序： ###

import java.util.Collection;
    import java.util.Comparator;
    import java.util.HashMap;
    import java.util.HashSet;
    import java.util.Iterator;
    import java.util.Map;
    import java.util.Scanner;
    import java.util.Set;
    import java.util.TreeSet;
    class Student implements Comparable<Student>{
        String name;
        int score;
    	public Student(String name, int score) {
    		super();
    		this.name = name;
    		this.score = score;
    	}
    	@Override
    	public String toString() {
    		// TODO Auto-generated method stub
    		return this.name+" "+this.score;
    	}
    	@Override
    	public int compareTo(Student b) {
    		int j = b.score - this.score;
    		if(j==0) {
    	return this.name.compareTo(b.name);
    		}
    		else
    			return j;
    	}
        
    }
    public class Main{
        public static void main(String[] args) {
        	Scanner cin = new Scanner(System.in);
        	Student [] s = {
        			new Student("skh",100),
        			new Student("xiaoming",98),
        			new Student("xiaohong",99),
        			new Student("azxx",100),
        			new Student("xh",99),
        			new Student("bz",100),
        			
        	};
        TreeSet <Student> set = new TreeSet<Student>();
        for(Student i:s) {
        	set.add(i);
        }
        for(Student i:set) {
        	System.out.println(i);
        }
       }     
    }

输出结果：

azxx 100
    bz 100
    skh 100
    xh 99
    xiaohong 99
    xiaoming 98