TreeSet，Comparator集合应用

最新推荐文章于 2023-04-30 14:34:59 发布

原创最新推荐文章于 2023-04-30 14:34:59 发布 · 416 阅读

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#TreeSet

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本文通过两个示例介绍如何使用Java中的TreeSet进行学生信息和教师信息的排序。第一个示例展示如何通过自定义比较器Comparator来实现对学生对象的分数和姓名排序；第二个示例则演示了实现Comparable接口的方法，按教师的编号和姓名进行排序。

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package com.sdtu.cn;

import java.util.Comparator;
import java.util.TreeSet;
import java.util.Iterator;
class Student{
String name;
int age;
float score;
public Student(String name, int age, float score) {
  super();
  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;
}

@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + ", score=" + score
+ "]";
}
static class StudentCompare implements Comparator {

  @Override
  public int compare(Object o1, Object o2) {
   Student s1 = (Student) o1;
   Student s2 = (Student) o2;
   int result = s1.score> s2.score?1:(s1.score==s2.score?0:-1);
   if(result == 0){
    result = s1.name.compareTo(s2.name);
   }
   return result;
  }

}

}
public class TreeSetTest {
public static void main(String[]args){
TreeSet ts = new TreeSet(new Student.StudentCompare());
ts.add(new Student("老五",21,90));
ts.add(new Student("老二",23,79));
ts.add(new Student("老四",24,71));
ts.add(new Student("老三",23,75));
ts.add(new Student("老大",25,78));
Iterator it = ts.iterator();
while(it.hasNext()){
  System.out.println(it.next());
}
}
}

第二种情况（参考网络）

import java.util.Iterator;
import java.util.*;

publicclass TreeSetTest {
publicstaticvoid main(String[] args) {
Set ts =new TreeSet();
ts.add(new Teacher("zhangsan",1));
ts.add(new Teacher("lisi",2));
ts.add(new Teacher("wangmazi",3));
ts.add(new Teacher("mazi",3));
Iterator it = ts.iterator();
while (it.hasNext()) {
System.out.println(it.next());
}
}
}

class Teacherimplements Comparable {
int num;
String name;

Teacher(String name, int num) {
this.num= num;
this.name= name;
}

public String toString() {
return"学好"+ num+"姓名"+ name;
}

publicint compareTo(Object o) {
Teacher ss = (Teacher) o;
int result= num> ss.num?1 : (num== ss.num? 0 :-1);
if (result==0) {
result = name.compareTo(ss.name);
}
return result;
}
}