JAVA菜鸟入门(18) Set的Iterator

1. 使用iterator遍历Set中元素

public class SetIteratorDemo {public static void main(String[] args) {HashSet<String> objectSet = new HashSet<String>();objectSet.add("white");objectSet.add("white");objectSet.add("green");objectSet.add("yellow");objectSet.add("blue");objectSet.add("Yellow");objectSet.add("red");objectSet.add("white");System.out.println("1 --------------------");for (String item : objectSet) {System.out.println(item);}System.out.println("2 --------------------");Iterator it = objectSet.iterator();while (it.hasNext()) {System.out.println(it.next());}}}

output:

1 --------------------redbluegreenYellowwhiteyellow2 --------------------redbluegreenYellowwhiteyellow

2. 使用Iterator 删除Set中元素

public class SetIteratorRemoveDemo {public static void main (String [] args) {// Set<Integer> numberSet = new HashSet<Integer>(); //works fine//Set numberSet = new HashSet(); //works fineHashSet numberSet = new HashSet(); //works finefor (int i = 0; i < 10; ++i) {numberSet.add(new Integer(i));}for (Iterator<Integer> it = numberSet.iterator(); it.hasNext(); ) {Integer a = it.next();if (a % 2 == 0) {it.remove(); // this actually differs from my habit.}}System.out.println(numberSet.toString());}}

output:

[1, 3, 5, 7, 9]

3. 

Set interface permits "null key" , so do HashSet, LinkedHashSet, TreeSet.