[LeetCode]Min Stack

class MinStack {    // stack: store the stack numbers    private Stack<Integer> stack = new Stack<Integer>();    // minStack: store the current min values    private Stack<Integer> minStack = new Stack<Integer>();    public void push(int x) {        // store current min value into minStack        if (minStack.isEmpty() || x <= minStack.peek())            minStack.push(x);        stack.push(x);    }    public void pop() {        // use equals to compare the value of two object, if equal, pop both of them        if (stack.peek().equals(minStack.peek()))            minStack.pop();        stack.pop();    }    public int top() {        return stack.peek();    }    public int getMin() {        return minStack.peek();    }}