JAVA集合之间的相互转换
程序员文章站
2022-05-25 08:29:55
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下面代码演示了List<-->数组、List<-->Set、数组<-->Set、Map将键转化为Set、Map将值转化为Set、Map将值转化为List等集合常用转化操作。
文章转自:http://jerval.iteye.com/blog/1001643
public class TestApp { public static void main(String[] args) { //List-->数组 List<String> list = new ArrayList<String>(); list.add("蹇伟"); list.add("Jerval"); list.add("杰威"); Object[] objects = list.toArray();//返回Object数组 System.out.println("objects:"+Arrays.toString(objects)); String[] strings1 = new String[list.size()]; list.toArray(strings1);//将转化后的数组放入已经创建好的对象中 System.out.println("strings1:"+Arrays.toString(strings1)); String[] strings2 = list.toArray(new String[0]);//将转化后的数组赋给新对象 System.out.println("strings2:"+Arrays.toString(strings2)); //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); //List-->Set List<String> list3 = new ArrayList<String>(new HashSet<String>()); //Set-->List Set<String> set = new HashSet<String>(new ArrayList<String>()); //数组-->Set String[] strs = {"AA","BB"}; Set<String> set2 = new HashSet<String>(Arrays.asList(strs)); System.out.println(set2); //Set-->数组 Set<String> set3 = new HashSet<String>(Arrays.asList("PP","OO")); String[] strSet = new String[set3.size()]; set3.toArray(strSet); System.out.println(Arrays.toString(strSet)); //Map操作 Map<String, String> map = new HashMap<String, String>(); map.put("YYY", "UUU"); map.put("RRR", "TTT"); // 将键转化为Set Set<String> mapKeySet = map.keySet(); // 将值转化为Set Set<String> mapValuesSet = new HashSet<String>(map.values()); // 将值转化为List List<String> mapValuesList = new ArrayList<String>(map.values()); } }
文章转自:http://jerval.iteye.com/blog/1001643
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