java各种集合类型相互转化

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-->ListString[] 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-->SetList<String> list3 = new ArrayList<String>(new HashSet<String>()); //Set-->ListSet<String> set = new HashSet<String>(new ArrayList<String>());//数组-->SetString[] 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());}}