TreeMap集合中怎么使用Comparator比较器呢？ - 黑马程序员技术交流社区

package com.test;
import java.util.*;
class Student {
private String name;
private int age;
public Student(String name, int age) {
this.name = name;
this.age = age;
}
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;
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + "]";
}
}
public class Test4 {
public static void main(String[] args) {
//Student stu = new Student("lisi", 20);
//System.out.println(stu);
//使用TreeMap可以传入比较器comparator
TreeMap<String, Student> className = new TreeMap<String,Student>(new MyComparator());
//建立班级容器(唯一性出问题)
className.put("class1",new Student("lisi",20));
className.put("class1", new Student("qinhaihang",18));
className.put("class2", new Student("haihangqin",19));
className.put("class2", new Student("hanghaiqin",17));
//使用迭代器打印键值
//将Map键存到Set集合中
Set<String> keyset = className.keySet();
Iterator<String> it = keyset.iterator();
while(it.hasNext()){
String key = it.next();
Student value = className.get(key);
System.out.println("Key:"+key+",Value:"+value);
}
}
}
class MyComparator implements Comparator<Object> {
@Override
public int compare(Object o1, Object o2) {
String s1 = (String)o1;
String s2 = (String)o2;
int num = s1.compareTo(s2);
if(num==0){
num=-1;
}
return num;
}
}

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