Java container notes

Import java. util. *; public class Test {public static void main (String [] args) throws Exception {Collection c = new HashSet (); c. add ("a"); c. add ("B"); Iterator I = c. iterator (); while (I. hasNext () {String value = (String) I. next (); System. out. println (value) ;}}print: a B/** boolean hasNext (); // determine whether the Object next () on the right of the cursor has an element (); // return the element on the right of the cursor and move the cursor to the next position void remove (); // Delete the element on the left, after executing next, this operation can only be executed once ** // ** remove () method */import java. util. *; public class Test {public static void main (String [] args) throws Exception {Collection c = new HashSet (); c. add (new Integer (1); c. add (new Integer (2); Iterator I = c. iterator (); while (I. hasNext () {Integer value = (Integer) I. next (); I. remove (); System. out. println (c) ;}}print: [2] []