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  • Java 集合转换(数组、List、Set、Map相互转换)

    转载自:http://blog.csdn.net/top_code/article/details/10552827

    代码:

    package com.example.test;
    
    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 {
    
        /**
         * @param args
         */
        public static void main(String[] args) {
            
            testList2Array();
            testArray2List();
            testSet2List();
            testList2Set();
            testSet2Array();
            testArray2Set();
            testMap2Set();
            testMap2List();
        }
    
        private static void testMap2List() {
            
            Map<String, String> map = new HashMap<String, String>();  
            map.put("A", "ABC");  
            map.put("K", "KK");  
            map.put("L", "LV");  
            
            // 将Map Key 转化为List    
            List<String> mapKeyList = new ArrayList<String>(map.keySet());  
            System.out.println("mapKeyList:"+mapKeyList);
            
            // 将Map Key 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);  
        }
    
    }

    完毕。

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  • 原文地址:https://www.cnblogs.com/zl0372/p/7514402.html
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