Javaセット変換【List配列、ListSet、配列Set、Map-->Set、Map-->List】

Javaセット間の相互変換
 
以下のコードは、List配列、ListSet、配列Set、MapがキーをSet、Mapに変換し、値をSet、Mapに変換し、値をListなどの集合に変換するための一般的な変換動作を示している。
 
 

public class TestApp {

	public static void main(String[] args) {
		//List-->  
		List list = new ArrayList();
		list.add("  ");
		list.add("Jerval");
		list.add("  ");
		Object[] objects = list.toArray();//  Object  
		System.out.println("objects:"+Arrays.toString(objects));
		String[] strings1 = new String[list.size()];
		list.toArray(strings1);//                  
		System.out.println("strings1:"+Arrays.toString(strings1));
		String[] strings2 = list.toArray(new String[0]);//            
		System.out.println("strings2:"+Arrays.toString(strings2));
		//  -->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());
		//  -->Set
		String[] strs = {"AA","BB"};
		Set set2 = new HashSet(Arrays.asList(strs));
		System.out.println(set2);
		//Set-->  
		Set set3 = new HashSet(Arrays.asList("PP","OO"));
		String[] strSet = new String[set3.size()];
		set3.toArray(strSet);
		System.out.println(Arrays.toString(strSet));
		//Map  
		Map map = new HashMap();
		map.put("YYY", "UUU");
		map.put("RRR", "TTT");
		//      Set  
		Set mapKeySet = map.keySet();
		//      Set  
		Set mapValuesSet = new HashSet(map.values());
		//      List  
		List mapValuesList = new ArrayList(map.values());

	}
}