实现一个特殊的栈，在实现栈的基本功能的基础上，再实现返回栈中最小元素的操作(java)

public static class MyStack1 {
        private Stack<Integer> stackData;
        private Stack<Integer> stackMin;

        public MyStack1() {
            this.stackData = new Stack<>();
            this.stackMin = new Stack<>();
        }

        public void push(int newNum) {
            // 处理min栈
            if (this.stackMin.isEmpty()) {
                this.stackMin.push(newNum);
            } else if (newNum <= this.getmin()) {
                this.stackMin.push(newNum);
            }

            // 处理data栈
            this.stackData.push(newNum);
        }

        public int pop() {
            if (this.stackData.isEmpty()) {
                throw new RuntimeException("Your stack is empty.");
            }

            // 弹出data栈的栈顶元素，如果此数和min栈的栈顶相等，min栈的栈顶也弹出
            int value = this.stackData.pop();
            if (value == this.getmin()) {
                this.stackMin.pop();
            }
            return value;
        }

        public int getmin() {
            if (this.stackMin.isEmpty()) {
                throw new RuntimeException("Your stack is empty.");
            }
            // 返回min栈的栈顶元素，但不弹出
            return this.stackMin.peek();
        }
    }