JAVA-常用集合型別轉換例子
阿新 • • 發佈:2020-10-05
package com.net.xinfang.reflect; 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; /*** * Array、Set、List、Map相互轉換 * */ public class ConvertorTest { /** * @param args */ public static void main(String[] args) { testList2Array();//List-Array testArray2List();//Array-List testSet2List();//Set-List testList2Set();//List-Set testSet2Array();//Set-Array testArray2Set();//Array-Set testMap2Set();//Map-Set testMap2List();//Map-List } private static void testMap2List() { Map<String, String> map = new HashMap<String, String>(); map.put("A", "ABC"); map.put("K", "KK"); map.put("L", "LV"); // 將Map Key 轉化為List List<String> mapKeyList = new ArrayList<String>(map.keySet()); System.out.println("mapKeyList:" + mapKeyList); // 將Map Key 轉化為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"); // 將Map 的鍵轉化為Set Set<String> mapKeySet = map.keySet(); System.out.println("mapKeySet:" + mapKeySet); // 將Map 的值轉化為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" }; // 陣列-->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-->陣列 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-->陣列 List<String> list = new ArrayList<String>(); list.add("AA"); list.add("BB"); list.add("CC"); Object[] objects = list.toArray();// 返回Object陣列 System.out.println("objects:" + Arrays.toString(objects)); String[] arr = new String[list.size()]; list.toArray(arr);// 將轉化後的陣列放入已經建立好的物件中 System.out.println("strings1:" + Arrays.toString(arr)); } private static void testArray2List() { // 陣列-->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); } }