java集合之间及数组相互转换方法

package com.collection.demo;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class ConvertorTest {

/**
* 集合之间相互转换
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
testMap2List();
testMap2Set();
testArray2Set();
testSet2Array();
testList2Set();
testSet2List();
testList2Array();
testArray2List();
}
private static void testMap2List(){
Map<String,String> map = new HashMap<String,String>();
map.put("A", "ABC");
map.put("K", "kk");
map.put("L", "LV");
//蒋map key转化为list
List<String> mapKeyList = new ArrayList<String>(map.keySet());
System.out.println("mapKeyList:"+mapKeyList);
//将Map value转化为list
List<String> mapValuesList = new ArrayList<String>(map.values());   
        System.out.println("mapValuesList:"+mapValuesList); 
}
private static void testMap2Set() { 
        
        Map<String, String> map = new HashMap<String, String>();   
        map.put("A", "ABC");   
        map.put("K", "KK");   
        map.put("L", "LV");   
         
        // 将Map 的键转化为Set     
        Set<String> mapKeySet = map.keySet();   
        System.out.println("mapKeySet:"+mapKeySet); 
         
        // 将Map 的值转化为Set     
        Set<String> mapValuesSet = new HashSet<String>(map.values());   
        System.out.println("mapValuesSet:"+mapValuesSet); 
    } 
private static void testArray2Set() { 
        
        String[] arr = {"AA","BB","DD","CC","BB"};   
         
        //数组-->Set   
        Set<String> set = new HashSet<String>(Arrays.asList(arr));   
        System.out.println(set);   
    } 
private static void testSet2Array() { 
        Set<String> set = new HashSet<String>(); 
        set.add("AA"); 
        set.add("BB"); 
        set.add("CC"); 
         
        String[] arr = new String[set.size()];   
        //Set-->数组   
        set.toArray(arr);  
        System.out.println(Arrays.toString(arr));   
    } 
private static void testList2Set() { 
        
        List<String> list = new ArrayList<String>(); 
        list.add("ABC"); 
        list.add("EFG"); 
        list.add("LMN"); 
        list.add("LMN"); 
         
        //List-->Set 
        Set<String> listSet = new HashSet<String>(list); 
        System.out.println(listSet); 
    } 
private static void testSet2List() { 
        
        Set<String> set = new HashSet<String>(); 
        set.add("AA"); 
        set.add("BB"); 
        set.add("CC"); 
         
        //Set --> List 
        List<String> setList = new ArrayList<String>(set); 
        System.out.println(setList);   
    } 
private static void testList2Array() { 
        //List-->数组   
        List<String> list = new ArrayList<String>();   
        list.add("AA");   
        list.add("BB");   
        list.add("CC");   
        Object[] objects = list.toArray();//返回Object数组   
        System.out.println("objects:"+Arrays.toString(objects));   
         
        String[] arr = new String[list.size()];   
        list.toArray(arr);//将转化后的数组放入已经创建好的对象中   
        System.out.println("strings1:"+Arrays.toString(arr));   
    }
private static void testArray2List() { 
        //数组-->List   
        String[] ss = {"JJ","KK"};   
        List<String> list1 = Arrays.asList(ss);   
        List<String> list2 = Arrays.asList("AAA","BBB");   
        System.out.println(list1);   
        System.out.println(list2);   
    } 
}