Map集合 键值对存在
Map在通过键取值时，取键，用set集合（无序的，不可重复的）
取值，用collection集合
map通过键来取值treemap集合：
Student：
public class student implements Comparable
private String name;
private int age;
public student() {
}
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 + "]";
}
@Override
public int compareTo(student o) {
// TODO Auto-generated method stub
int a=this.age-o.age;
//姓名如果相等 ，重新调用这个方法，来比较名字
int a1=this.name.compareTo(name);
return a==0? a1:a;
}
}
Demo1：
public class Demo1 {
public static void main(String[] args) {
//对name age 的对象进行夫赋值
student stu1=new student("张三",11);
student stu2=new student("李四",50);
student stu3=new student("赵五",34);
student stu4=new student("王六",23);
TreeMap
map.put(stu1, "唱歌");
map.put(stu2, "跳舞");
map.put(stu3, "绘画");
map.put(stu4, "跳高");
System.out.println(map);//注意，会报错
//对象需要重写compareoTo方法
//{student [name=张三, age=11]=唱歌,
// student [name=王六, age=23]=跳高,
// student [name=赵五, age=34]=绘画,
// student [name=李四, age=50]=跳舞}
}
}