将Map中的key和values转化为List

短命女 2022-08-12 00:29 500阅读 0赞

在项目开发中，常常会用到Map，而map的存放是无序的，它存放的是键值对，也就是一个键对应一个值。有时需要将Map的key和value转化为List来进行相关的操作，现在通过实例来实现Map的key和value的转化。

代码如下：

package com.example;
    
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.HashSet;
    import java.util.Iterator;
    import java.util.List;
    import java.util.Map;
    import java.util.Set;
    
    public class JavaTest {
    	public static void main(String[] args) {
    
    		Map<String, String> myMap = new HashMap<String, String>();
    		myMap.put("a", "张三");
    		myMap.put("b", "李四");
    		myMap.put("c", "王五");
    		myMap.put("d", "小六");
    
    		Set<String> set = getKeySetByMap(myMap);
    
    		List<String> keyListBySet = getKeyListBySet(set);
    
    		List<String> keyList = getListByMap(myMap, true);
    		List<String> valuesList = getListByMap(myMap, false);
    
    		Iterator<String> it = set.iterator();
    
    		while (it.hasNext()) {
    			String key = it.next().toString();
    			System.out.println("set:" + key);
    		}
    		for (int i = 0; i < keyListBySet.size(); i++) {
    
    			System.out.println("keyListBySet:" + i + "->" + keyListBySet.get(i)
    					+ ";key:" + keyList.get(i) + ";values:"
    					+ valuesList.get(i));
    
    		}
    
    	}
    
    	/**
    	 * 根据map获取map包含的key,返回set
    	 * 
    	 * @param map
    	 * @return
    	 */
    	public static Set<String> getKeySetByMap(Map<String, String> map) {
    
    		Set<String> keySet = new HashSet<String>();
    		keySet.addAll(map.keySet());
    
    		return keySet;
    	}
    
    	/**
    	 * 根据key的set返回key的list
    	 * 
    	 * @param set
    	 * @return
    	 */
    	public static List<String> getKeyListBySet(Set<String> set) {
    		List<String> keyList = new ArrayList<String>();
    		keyList.addAll(set);
    		return keyList;
    	}
    
    	/**
    	 * 根据map返回key和value的list
    	 * 
    	 * @param map
    	 * @param isKey
    	 *            true为key,false为value
    	 * @return
    	 */
    	public static List<String> getListByMap(Map<String, String> map,
    			boolean isKey) {
    		List<String> list = new ArrayList<String>();
    
    		Iterator<String> it = map.keySet().iterator();
    		while (it.hasNext()) {
    			String key = it.next().toString();
    			if (isKey) {
    				list.add(key);
    			} else {
    				list.add(map.get(key));
    			}
    		}
    
    		return list;
    	}
    
    }

输出结果如下：

set:d
    set:b
    set:c
    set:a
    keyListBySet:0->d;key:d;values:小六
    keyListBySet:1->b;key:b;values:李四
    keyListBySet:2->c;key:c;values:王五
    keyListBySet:3->a;key:a;values:张三