map排序及keyset顺序问题

package test;

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.TreeMap;

public class testKeySetSort {
  public static void main(String[] args) {
    System.out.println("## HashTable --降序  ##");
    Hashtable<String, String> ht = new Hashtable<String, String>();
    ht.put("c1","000");
    ht.put("a3","000");
    ht.put("c2","000");
    ht.put("c5","000");
    ht.put("c4","000");
    
    Iterator<String> it = ht.keySet().iterator();
    while(it.hasNext()) {
      System.out.println(it.next());
    }
    
    System.out.println("## TreeMap --升序  ##");
    TreeMap<String,String> tm = new TreeMap<String,String>();
    tm.put("c1","000");
    tm.put("a3","000");
    tm.put("c2","000");
    tm.put("c5","000");
    tm.put("c4","000");
    
    Iterator<String> it2 = tm.keySet().iterator();
    while(it2.hasNext()) {
      System.out.println(it2.next());
    }
    
    System.out.println("## HashMap --乱序  ##");
    Map<String, String> hm = new HashMap<String, String>();
    hm.put("c1","000");
    hm.put("a3","000");
    hm.put("c2","000");
    hm.put("c5","000");
    hm.put("c4","000");
    
    Iterator<String> it3 = hm.keySet().iterator();
    while(it3.hasNext()) {
      System.out.println(it3.next());
    }
    
    System.out.println("## LinkedHashMap --原序  ##");
    LinkedHashMap<String, String> lhm = new LinkedHashMap<String, String>();
    lhm.put("c1","000");
    lhm.put("a3","000");
    lhm.put("c2","000");
    lhm.put("c5","000");
    lhm.put("c4","000");
    Iterator<String> it4 = lhm.keySet().iterator();
    while(it4.hasNext()) {
      System.out.println(it4.next());
    }   
  }
}

输出：