Stack and Queue imp function and iterator

import java.util.*; public class Main { public static boolean main(String[] args) { Stack s = new Stack(); // stack definition s.push('7'); s.push('9'); s.peek(); s.pop(); System.out.println("s.contains" + s.contains(s.peek())); System.out.println("s.peek:" + s.contains('1')); System.out.println("s.indexOf(9);"+s.indexOf('9')); // only available to Stack start from 0 System.out.println(s.isEmpty()); Iterator i = s.iterator(); // iterator for stack while(i.hasNext()) { System.out.println(i.next()); // i.next() is point to current variable and after execution goes to next element } Queue Q= new LinkedList(); // Q definition Q.add('1'); Q.add('2'); Q.add('3'); Q.add('4'); Q.add('5'); System.out.println("q.contains"+Q.contains('1')); // contains work System.out.println("q.peek:" + (Q.peek())); System.out.print(Q.isEmpty()); Iterator i2 = Q.iterator(); while (i2.hasNext()) //iterator for Queue { System.out.println("i2 value :"); System.out.print(i2.next()); } double[] myList ={0.1,0.2}; // array initialization for (double element: myList) { System.out.println(element); } return true; } } //summary : // Stack s = new Stack(); // Stack operation: push() ,pop(),peek(),contains(),indexof(),isEmpty() // Queue q = new Linklist(); // Operation : add(),remove(),contains(),peek(),isEmpty() // indexof(won't allow) // Iterator i = s.iterator; // see Caps Iterator and small iterator // while(i.hasNext()) { System.out.println(i.next()}) // only i.next() works. // type cast after stack.pop() as it return the object.