Map的实现类：TreeMap

1.存储结构：红黑树

2.实现了SortedMap接口（是Map的子接口），可以对key自动排序。

3.实例代码：Student类和Demo03

如果出现类转换异常参考【TreeSet（红黑树）】

package com.map;import java.util.Objects;public class Student implements Comparable<Student>{private String name;private int stuNo;public Student(String name, int stuNo) {this.name = name;this.stuNo = stuNo;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getStuNo() {return stuNo;}public void setStuNo(int stuNo) {this.stuNo = stuNo;}@Overridepublic String toString() {return "Student [name=" + name + ", stuNo=" + stuNo + "]";}@Overridepublic int compareTo(Student o) {int n1 = this.getStuNo()-o.getStuNo();int n2 = this.name.compareTo(o.getName());return n1==0?n1:n2;}
}

package com.map;import java.util.Map;
import java.util.Set;
import java.util.TreeMap;/*** TreeMap集合的使用* 存储结构：红黑树*/
public class Demo03 {public static void main(String[] args) {//创建集合TreeMap<Student, String> treeMap = new TreeMap<>();//创建学生对象Student s1 = new Student("小王", 100);Student s2 = new Student("小刘", 101);Student s3 = new Student("小方", 102);Student s4 = new Student("小舟", 103);//1添加数据treeMap.put(s1,"北京");treeMap.put(s2,"上海");treeMap.put(s3,"福建");treeMap.put(s4,"重庆");System.out.println("学生个数："+treeMap.size());System.out.println(treeMap);//2删除数据treeMap.remove(s1);System.out.println(treeMap);//3遍历数据System.out.println("--------keySet()-----------");Set<Student> set = treeMap.keySet();for(Student s : set){System.out.println(s);}System.out.println("--------entrySet()-----------");Set<Map.Entry<Student, String>> entries = treeMap.entrySet();for(Map.Entry<Student, String> entry : entries){System.out.println(entry.getKey()+" "+entry.getValue());}}
}

结果：