/**
TreeMap练习
根据年龄排序。
根据姓名排序:
*/
import java.util.*;
class StuNameComparator implements Comparator<Student>
{
//复写compare方法
public int compare(Student s1,Student s2)
{
int num= s1.getName().compareTo(s2.getName());
if (num==0)
{
return new Integer(s1.getAge()).compareTo(new Integer(s2.getAge()));
}
return num;
}
}
class TreeMapTest
{
public static void main(String[] args)
{
TreeMap<Student,String > tm=new TreeMap<Student,String >(new StuNameComparator());//TreeMap可以将比较器传递到其对象内
tm.put(new Student("zhangsan01",24),"beijing");
tm.put(new Student("zhangsan04",32),"shenzheng");
tm.put(new Student("zhangsan03",23),"shenzheng");
tm.put(new Student("zhangsan02",20),"shnghai");
//tm.put(new Student("zhangsan03",32),"shenzheng");
//使用entrySet遍历
Set<Map.Entry<Student,String>> entryset=tm.entrySet();
Iterator<Map.Entry<Student,String>> it=entryset.iterator();
while (it.hasNext())
{
Map.Entry<Student,String> map=it.next();
Student key=map.getKey();
String value=map.getValue();
System.out.println(key+"=="+value);
}
}
}
创建学生类,定义一个比较器。<pre name="code" class="java">class Student implements Comparable<Student>//比较学生
{
private String name;
private int age;
Student(String name ,int age){
this.name=name;
this.age=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 int hashCode(){
return this.name.hashCode()+age*34;
}
public boolean equals(Object obj){
//判断类型是否相同
if (!(obj instanceof Student))
{
throw new ClassCastException("类型不同");
}
Student s=(Student)obj;
return this.name.equals(s.name) && this.age==s.age;
}
public String toString(){
return name+":"+age;
}
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;
}
}