content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you 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 org.apache.calcite.util;
  
  import java.util.List;
  
  /**
   * Utilities to make vanilla lists look like stacks.
   */
  @Deprecated // to be removed before 2.0
  public class Stacks {
    private Stacks() {
    }
  
    /**
     * Returns the most recently added element in the stack. Throws if the
     * stack is empty.
     */
    public static <T> T peek(List<T> stack) {
      return stack.get(stack.size() - 1);
    }
  
    /**
     * Returns the {@code n}th most recently added element in the stack.
     * Throws if the stack is empty.
     */
    public static <T> T peek(int n, List<T> stack) {
      return stack.get(stack.size() - n - 1);
    }
  
    /**
     * Adds an element to the stack.
     */
    public static <T> void push(List<T> stack, T element) {
      stack.add(element);
    }
  
    /**
     * Removes an element from the stack. Asserts of the element is not the
     * one last added; throws if the stack is empty.
     */
    public static <T> void pop(List<T> stack, T element) {
      assert stack.get(stack.size() - 1) == element;
      stack.remove(stack.size() - 1);
    }
  
    /**
     * Removes an element from the stack and returns it.
     *
     * <p>Throws if the stack is empty.
     */
    public static <T> T pop(List<T> stack) {
      return stack.remove(stack.size() - 1);
    }
  }
  