java HashMap,TreeMap与LinkedHashMap的详解

package Map; 
 
import java.util.*; 
 
public class HashMaps { 
  public static void main(String[] args) { 
    Map map = new HashMap(); 
    map.put("a","aaa"); 
    map.put("b","bbb"); 
    map.put("c","ccc"); 
    map.put("d","ddd"); 
 
    Iterator iterator = map.keySet().iterator(); 
    while (iterator.hasNext()) { 
      Object key = iterator.next(); 
      System.out.println("map.get(key) is :" + map.get(key)); 
    } 
 
    Hashtable tab = new Hashtable(); 
    tab.put("a","aaa"); 
    tab.put("b","bbb"); 
    tab.put("c","ccc"); 
    tab.put("d","ddd"); 
    Iterator 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 tmp = new TreeMap(); 
    tmp.put("a","aaa"); 
    tmp.put("b","bbb"); 
    tmp.put("c","ccc"); 
    tmp.put("d","ddd"); 
    tmp.put("a","aba"); 
    Iterator iterator_2 = tmp.keySet().iterator(); 
    while (iterator_2.hasNext()) { 
      Object key = iterator_2.next(); 
      System.out.println("tmp.get(key) is :" + tmp.get(key)); 
    } 
     
     
    LinkedHashMap<String,Integer> linkedHashMap = new LinkedHashMap<String,Integer>(); 
    linkedHashMap.put("dasdsa",1); 
    linkedHashMap.put("gdsf",2); 
    linkedHashMap.put("texvdfd",3); 
    linkedHashMap.put("bdada",4); 
     
    linkedHashMap.put("gdsf",3); 
    for(String temp : linkedHashMap.keySet()){ 
      System.out.println(temp); 
    } 
     
  } 
 
}