TreeMap自定义对象存取练习 - 黑马程序员技术交流社区

import java.util.*;
//主类
public class TreeMapTest
{
public static void sop(Object obj)
{
System.out.println(obj);
}
public static void main(String[] args)
{
//1 创建TreeMap映射对象
//TreeMap<Student,String> tm = new TreeMap<Student,String>(new StuNameComparator());//姓名字典序排序
TreeMap<Student,String> tm = new TreeMap<Student,String>();//年龄升序排序
//2 添加Student对象
tm.put(new Student("Jack",25),"北京");
tm.put(new Student("Jack",22),"北京");
tm.put(new Student("Mike",22),"天津");
//sop(tm.put(new Student("Mike",22),"淮南"));//注意了，如果Student相同，但是地址不相同，根据put方法，新地址会覆盖原来的地址
tm.put(new Student("Jimmy",21),"上海");
tm.put(new Student("Jakie",20),"广州");
tm.put(new Student("David",17),"长沙");
tm.put(new Student("Tom",26),"连云港");
//第一种方式取出所有键值
sop("第一种方式取出所有键值");
getWay(tm);
//第二种方式取出所有键值
//sop("第二种方式取出所有键值");
//getWay_2(tm);
}
//第一种方式迭代取出所有键值
public static void getWay(TreeMap<Student,String> tm)
{
//1 把所有key存入set
Set<Student> keySet = tm.keySet();
//2 获取迭代器
for(Iterator<Student> it = keySet.iterator(); it.hasNext(); )
{
//3 迭代取出key
Student stu = it.next();
//4 通过key获取value
String addr = tm.get(stu);
//打印取出结果
sop(stu.toString()+".........."+addr);
}
}
//第二种方式迭代取出所有键值
public static void getWay_2(TreeMap<Student,String> tm)
{
//1 把所有映射项存入Map.Entry
Set<Map.Entry<Student,String>> entry = tm.entrySet();
//2 获取迭代器
for(Iterator<Map.Entry<Student,String>> it = entry.iterator(); it.hasNext(); )
{
//3 迭代取出映射项
Map.Entry<Student,String> me = it.next();
//4 利用Map.Entry中的get方法获取key和value
Student stu = me.getKey();
String addr = me.getValue();
//5打印取出结果
sop(stu.toString()+"***********"+addr);
}
}
}
//学生姓名比较器类
class StuNameComparator implements Comparator<Student>
{
//覆盖compare方法
public int compare(Student stu1,Student stu2)
{
//先按姓名排序，如果相同再按年龄升序排序
int num = stu1.getName().compareTo(stu2.getName());
if(num == 0)
return new Integer(stu1.getAge()).compareTo(new Integer(stu2.getAge()));
//否则就按按姓名排序
return num;
}
}
//学生类
class Student implements Comparable<Student>
{
private String name;
private int age;
//构造函数初始化学生
Student(String name,int age)
{
this.name = name;
this.age = age;
}
public int compareTo(Student stu)
{
//按学生的年龄排序，如果年龄相等就按姓名字典序排序
int num = new Integer(this.getAge()).compareTo(new Integer(stu.getAge()));
if(num == 0)
return this.getName().compareTo(stu.getName());
//否则就按年龄排序
return num;
}
//计算学生对象的哈希地址
public int hashCode()
{
return name.hashCode()+age*37;
}
public boolean equals(Object obj)
{
//如果不是学生对象，抛出类型转换异常
if(!(obj instanceof Student))
throw new ClassCastException("不能转换成Student类型");
//类型转换
Student stu = (Student)obj;
//比较学生对象姓名和年龄，去除重复元素
return this.getName().equals(stu.getName()) && this.getAge()==stu.getAge();
}
public void setName(String name)
{
this.name =name;
}
public String getName()
{
return name;
}
public void setAge(int age)
{
this.age = age;
}
public int getAge()
{
return age;
}
public String toString()
{
return name+"....."+age;
}
}

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