Java 集合转换(数组、List、Set、Map相互转换)

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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);  }}
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