作者:Lyj眼淚啲菋噵 | 来源:互联网 | 2023-05-17 13:50
Java集合转换【List<-->数组、List<-->Set、数组<-->Set、Map-->Set、Map-->List】
//List-->数组
List list = new ArrayList();
list.add("tom");
list.add("Jerval");
list.add("WeiSi");
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 list1 = Arrays.asList(ss);
List list2 = Arrays.asList("AAA","BBB");
System.out.println(list1);
System.out.println(list2);
//List-->Set
List list3 = new ArrayList(new HashSet());
//Set-->List
Set set = new HashSet(new ArrayList());
//数组-->Set
String[] strs = {"AA","BB"};
Set set2 = new HashSet(Arrays.asList(strs));
System.out.println(set2);
//Set-->数组
Set set3 = new HashSet(Arrays.asList("PP","OO"));
String[] strSet = new String[set3.size()];
set3.toArray(strSet);
System.out.println(Arrays.toString(strSet));
//Map操作
Map map = new HashMap();
map.put("YYY", "UUU");
map.put("RRR", "TTT");
// 将键转化为Set
Set mapKeySet = map.keySet();
// 将值转化为Set
Set mapValuesSet = new HashSet(map.values());
// 将值转化为List
List mapValuesList = new ArrayList(map.values());