/*
 * Copyright 2014 NAVER Corp.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.navercorp.pinpoint.web.util;

import java.util.LinkedList;

/**
 * @author emeroad
 */
public class Stack<T> {

    private final LinkedList<T> stack = new LinkedList<>();

    public void push(T obj) {
        if (obj == null) {
            throw new NullPointerException("obj must not be null");
        }

        stack.add(obj);
    }

    public T getLast() {
        return stack.getLast();
    }

    public T pop() {
        return stack.pollLast();
    }

    public T getParent() {
        final int parent = stack.size() - 2;
        if (parent < 0) {
            return null;
        }
        return stack.get(parent);
    }

    public int size() {
        return stack.size();
    }
    
    public T get(int index) {
        return stack.get(index);
    }
    
    @Override
    public String toString() {
        return "Stack{" +
                "stack=" + stack +
                '}';
    }
}