Java code please

System.out.println(Recursion.indexOf("Hello", "lo")); // 3 Stack stack = new Stack(); stack.push(2); stack.push(3); stack.push(4); stack.push(55); stack.push(6); stack.push(17); stack.push(8); System.out.println(Recursion.removeEvenNumbers(stack, 2)); // 2 System.out.println(stack); // [2, 3, 4, 55, 17] System.out.println(Recursion.evenDigits(-1364035)); // 640 String expr = "(((1+2)*(3+1))+(1*(2+2)))"; Queue q = new LinkedList(); for (char ch: expr.toCharArray()) { q.add(ch); } System.out.println(Recursion.evaluate(q)); // 16 System.out.println(stack); // [2, 3, 4, 55, 17] Recursion.repeatStack(stack); System.out.println(stack); // [2, 2, 3, 3, 4, 4, 55, 55, 17, 17] Queue q2 = new LinkedList(); q2.add(34); q2.add(15); q2.add(0); Recursion.doubleElements(q2); System.out.println(q2); [68, 30, 0]

/** * Write a recursive function that accepts a Queue. It * should change every int in this queue to be double its original * value. You may NOT use loops or any other data structures besides 2 * the queue passed in as a parameter. You may use a helper function. * @param a */ public static void doubleElements (Queue q) {}