class MyQueue { Stack<Integer> stack1; Stack<Integer> stack2; /** Initialize your data structure here. */ public MyQueue() { stack1=new Stack<>(); stack2=new Stack<>(); } /** Push element x to the back of queue. */ public void push(int x) { stack1.push(x); } /** Removes the element from in front of queue and returns that element. */ public int pop() { if(empty()){ return -1; } if(stack2.isEmpty()){ while(!stack1.isEmpty()){ stack2.push(stack1.pop()); } } return stack2.pop(); } /** Get the front element. */ public int peek() { if(stack2.isEmpty()){ while(!stack1.isEmpty()){ stack2.push(stack1.pop()); } } return stack2.peek(); } /** Returns whether the queue is empty. */ public boolean empty() { return stack1.isEmpty()&&stack2.isEmpty(); } } /** * Your MyQueue object will be instantiated and called as such: * MyQueue obj = new MyQueue(); * obj.push(x); * int param_2 = obj.pop(); * int param_3 = obj.peek(); * boolean param_4 = obj.empty(); */