Java【力扣155】最小栈

class MinStack {
    private Stack<Integer> s1=new Stack<>();
    private Stack<Integer> s2=new Stack<>();
    public MinStack() {
    }
    public void push(int val) {
        s1.push(val);
        if(s2.isEmpty()){
            s2.push(val);
        }else {
            int temp=s2.peek();
            s2.push(Math.min(temp,val));
        }
    }
    public void pop() {
        s1.pop();
        s2.pop();
    }
    public int top() {
        return s1.peek();
    }
    public int getMin() {
        return s2.peek();
    }
}
/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack obj = new MinStack();
 * obj.push(val);
 * obj.pop();
 * int param_3 = obj.top();
 * int param_4 = obj.getMin();
 */