集合 TreeSet HashMap

SetTest类：

package com.jinhuapkg;

import java.util.Iterator;
import java.util.TreeSet;

public class SetTest {

    public static void main(String[] args){
        TreeSet treeSet = new TreeSet();
        treeSet.add("hello");
        treeSet.add("hi");
        treeSet.add("well");
        treeSet.add("ok");

        Iterator iterator = treeSet.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());
        }
        }
}

MapTest类：

package com.jinhuapkg;

import java.util.HashMap;

public class MapTest {

    public static void main(String[] args) {
        HashMap hashMap = new HashMap();
        hashMap.put("1", "aaa");
        hashMap.put("2", "bbb");
        System.out.println(hashMap.get("1"));
    }

}