Java中HashMap和TreeMap的区别深入理解

package com.hephec.Map;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;

class HahsMaps
{
public static void main(String[] args)
{
Map<String,String> map=new HashMap<String,String>();
map.put("a","aaa");
map.put("b","bbb");
map.put("c","ccc");
map.put("d","ddd");
Iterator<String> iterator=map.keySet().iterator();
while(iterator.hasNext()){
Object key=iterator.next();
System.out.println("map.get(key) is:"+map.get(key));
}
//定义HashTable，用来测试
Hashtable<String,String> tab=new Hashtable<String,String>();
tab.put("a","aaa");
tab.put("b","bbb");
tab.put("c","ccc");
tab.put("d","ddd");
Iterator<String> iterator_1=tab.keySet().iterator();
while(iterator_1.hasNext()){
Object key=iterator_1.next();
System.out.println("tab.get(key) is:"+tab.get(key));
}
TreeMap<String,String> tmp=new TreeMap<String,String>();
tmp.put("a","aaa");
tmp.put("b","bbb");
tmp.put("c","ccc");
tmp.put("d","ddd");
Iterator<String> iterator_2=tmp.keySet().iterator();
while(iterator_2.hasNext()){
Object key=iterator_2.next();
System.out.println("tmp.get(key) is:"+tmp.get(key));
}
}
}