关于Map集合中键的唯一性的问题 - 黑马程序员技术交流社区

import java.util.*;
class Student implements Comparable<Student>
{
String name;
int age;
Student(String name,int age)
{
this.name=name;
this.age=age;
}
public String getName()
{
return name;
}
public int getAge()
{
return age;
}
public int compareTo(Student s)
{
int num=new Integer(this.age).compareTo(new Integer(s.age));
if(num==0)
return this.name.compareTo(s.name);
return num;
}
public String toString()
{
return this.name+":"+this.age;
}
}
class MapTest2
{
public static void main(String[] args)
{
TreeMap<Student,String> tm=new TreeMap<Student,String>();
tm.put(new Student("lisi03",23),"nanjing");
tm.put(new Student("lisi04",24),"wuhan");
tm.put(new Student("lisi01",21),"beijing");
tm.put(new Student("lisi01",21),"tianjin");
tm.put(new Student("lisi02",22),"shanghai");
Set<Student> keyset=tm.keySet();
Iterator<Student> it=keyset.iterator();
while(it.hasNext())
{
Student s1=it.next();
String addr=tm.get(s1);
sop(s1+":"+addr);
}
}
public static void sop(Object obj)
{
System.out.println(obj);
}
}

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public class StuNameComparator implements Comparator<Student> {
/*按照姓名排序，如果姓名相同，那么按照年龄排序*/
public int compare(Student o1, Student o2) {
int num = o1.getName().compareTo(o2.getName());
if (num == 0) {
return o1.getAge() - o2.getAge();
}
return num;
}
}
public class Student /*implements Comparable<Student> */{// 十七具有比较性，防止排序的出现异常
private String name;// 姓名
private int age;// 年龄
public Student(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
// /* 重写hashCode()方法 */
// public int hashCode() {
// return this.name.hashCode() + this.age * 12;
// }
//
// /* 重写equals方法 */
// public boolean equals(Object ob) {
// if (!(ob instanceof Student))
// throw new ClassCastException("不是Student对象");
// Student stu = (Student) ob;
// return this.name.equals(stu.getName()) && this.age == stu.getAge();
//
// }
//
// /*
// * 覆写CompareTo方法先比较年龄，然后比较姓名
// */
// public int compareTo(Student stu) {
// int num = this.age - stu.age;
// if (num == 0) {
// return this.name.compareTo(stu.name);
// }
// return num;
//
// }
}
public class TreeMapDemo {
public static void main(String[] args) {
/* 定义HashMap，里面存储的是Student和地址 */
TreeMap<Student, String> map = new TreeMap<Student, String>(new StuNameComparator());
map.put(new Student("java03", 23), "北京");
map.put(new Student("net02", 21), "上海");
map.put(new Student("net03", 26), "广州");
map.put(new Student("java01", 24), "南京");
map.put(new Student("net03", 26), "广州");
Set<Student> set = map.keySet();
Iterator<Student> it = set.iterator();
while (it.hasNext()) {
Student stu = it.next();
String name = stu.getName();
int age = stu.getAge();
String address = map.get(stu);
System.out.println(name + ":" + age + ":" + address);
}
}
}
public class TreeMapDemo {
public static void main(String[] args) {
/* 定义HashMap，里面存储的是Student和地址 */
TreeMap<Student, String> map = new TreeMap<Student, String>(new StuNameComparator());
map.put(new Student("java03", 23), "北京");
map.put(new Student("net02", 21), "上海");
map.put(new Student("net03", 26), "广州");
map.put(new Student("java01", 24), "南京");
map.put(new Student("net03", 26), "广州");
Set<Student> set = map.keySet();
Iterator<Student> it = set.iterator();
while (it.hasNext()) {
Student stu = it.next();
String name = stu.getName();
int age = stu.getAge();
String address = map.get(stu);
System.out.println(name + ":" + age + ":" + address);
}
}
}

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