TreeMap

TreeMap是通过二叉树的原理来保证键的唯一性。

package study;
import java.util.*;
public class Example33 {
public static void main(String[] args) {
TreeMap tm=new TreeMap(new MyComparator3());
tm.put("1","Jack");
tm.put("2","Rose");
tm.put("3","Lucy");
Set keySet=tm.keySet();
Iterator it=keySet.iterator();
while(it.hasNext()){
Object key=it.next();
Object value=tm.get(key);
System.out.println(key+":"+value);
}
}
}
class MyComparator3 implements Comparator{
public int compare(Object obj1,Object obj2){
String id1=(String)obj1;
String id2=(String)obj2;
return id2.compareTo(id1);
}
}