java集合之三映射：HashMap、Hashtable、LinkedHashMap、TreeMap

package com.jdk7.chapter4;

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

/**
 * 集合之形式三》映射(Map),根据键得到值，不允许'键'重复,允许'值'重复,包含HashMap、HashTable、LinkedHashMap、TreeMap
 * HashMap：允许最多一个'键'为null，多个'值'为null; 不支持线程同步(即多个线程可以同时写HashMap)
 * HashTable：不允许键或值为null，支持线程同步(即同一时刻只能一个线程写HashTable)
 * LinkedHashMap：保存记录的插入顺序，先插入的记录会先得到，允许最多一个'键'为null，多个'值'为null
 * TreeMap：按键升序排列，不允许'键'为null，允许多个'值'为null
 * @author Administrator
 *
 */
public class MapTest {
    public static void init(Map map){
        if(map==null){
            System.out.println("映射不能为空！");
        }
        map.put("001", "Hello");
        map.put("002", "Lily");
        map.put("003", "Lucy");
        map.put("004", "Hanmei");
    }
    public static void printMap(Map map){
        if(map==null){
            System.out.println("映射为空");
        }
        //先获取Map的所有键，获取的键值为无重复的Set，再依次遍历key集合
        Iterator it = map.keySet().iterator();
        Object key = null;
        Object value = null;
        System.out.println("=======遍历key=======");
        while(it.hasNext()){
            key = it.next();
            value = map.get(key);
            System.out.println("key: "+key+" value: "+value);
        }
        
        Iterator itentry = map.entrySet().iterator();
        Map.Entry entry = null;
        System.out.println("=======遍历集合中的每条记录=======");
        while(itentry.hasNext()){
            entry = (Map.Entry)itentry.next();
            System.out.println("key: "+entry.getKey()+" value: "+entry.getValue());
        }
        System.out.println();
    }
    
    public static boolean containsKey(Map map, Object obj){
        if(map==null){
            return false;
        }
        return map.containsKey(obj);
    }
    
    public static boolean containsValue(Map map, Object obj){
        if(map==null){
            return false;
        }
        return map.containsValue(obj);
    }
    /**
     * 
     * @param map
     
    public static void add(Map map){
        MapTest.init(map);
        System.out.println("Map中是否包含Key>"+MapTest.containsKey(map, null));
        System.out.println("Map中是否包含Value>"+MapTest.containsValue(map, "2222"));
        map.put(null, "4444");
        map.put(null, "2222");
        map.put("005", null);
        map.put("006", null);
        MapTest.printMap(map);
    }
    */
    public static void add(Map map,Object key, Object value){
        MapTest.init(map);
        if(!(MapTest.containsKey(map, key) && MapTest.containsValue(map, value))){
            map.put(key, value);
        }
    }
    
    public static void HashMap(){
        System.out.println("===============HashMap映射===============");
        Map map = new HashMap();
        MapTest.add(map, null, "4444");
        MapTest.add(map, null, "2222");
        MapTest.add(map, "005", null);
        MapTest.add(map, "006", null);
        MapTest.printMap(map);
    }
    
    public static void HashTable(){
        System.out.println("===============HashTable映射===============");
        Map map = new Hashtable();
        MapTest.init(map);
        Object key = "005";
        Object value = "700";
        if(!(MapTest.containsKey(map, key) && MapTest.containsValue(map, value))){
            map.put(key, value);
        }
        MapTest.printMap(map);
    }
    
    public static void linkedHashMap(){
        System.out.println("===============linkedHashMap映射===============");
        Map map = new java.util.LinkedHashMap();
        MapTest.add(map, null, "4444");
        MapTest.add(map, null, "2222");
        MapTest.add(map, "005", null);
        MapTest.add(map, "006", null);
        MapTest.printMap(map);
    }
    
    public static void treeMap(){
        System.out.println("===============treeMap映射===============");
        Map map = new TreeMap();
        MapTest.init(map);
        Object key = "005";
        Object value = null;
        if(!(MapTest.containsKey(map, key) && MapTest.containsValue(map, value))){
            map.put(key, value);
        }
        MapTest.printMap(map);
    }
    public static void main(String[] args) {
        MapTest mt = new MapTest();
        mt.HashMap();
        mt.HashTable();
        mt.linkedHashMap();
        mt.treeMap();
    }
}

执行结果：
===============HashMap映射===============
=======遍历key=======
key: null value: 2222
key: 004 value: Hanmei
key: 005 value: null
key: 006 value: null
key: 001 value: Hello
key: 002 value: Lily
key: 003 value: Lucy
=======遍历集合中的每条记录=======
key: null value: 2222
key: 004 value: Hanmei
key: 005 value: null
key: 006 value: null
key: 001 value: Hello
key: 002 value: Lily
key: 003 value: Lucy

===============HashTable映射===============
=======遍历key=======
key: 005 value: 700
key: 004 value: Hanmei
key: 003 value: Lucy
key: 002 value: Lily
key: 001 value: Hello
=======遍历集合中的每条记录=======
key: 005 value: 700
key: 004 value: Hanmei
key: 003 value: Lucy
key: 002 value: Lily
key: 001 value: Hello

===============linkedHashMap映射===============
=======遍历key=======
key: 001 value: Hello
key: 002 value: Lily
key: 003 value: Lucy
key: 004 value: Hanmei
key: null value: 2222
key: 005 value: null
key: 006 value: null
=======遍历集合中的每条记录=======
key: 001 value: Hello
key: 002 value: Lily
key: 003 value: Lucy
key: 004 value: Hanmei
key: null value: 2222
key: 005 value: null
key: 006 value: null

===============treeMap映射===============
=======遍历key=======
key: 001 value: Hello
key: 002 value: Lily
key: 003 value: Lucy
key: 004 value: Hanmei
key: 005 value: null
=======遍历集合中的每条记录=======
key: 001 value: Hello
key: 002 value: Lily
key: 003 value: Lucy
key: 004 value: Hanmei
key: 005 value: null