Character Stack : Stack « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. Stack

/*******************************************************************************
 * Copyright (c) 2008 xored software, Inc.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     xored software, Inc. - initial API and Implementation (Alex Panchenko)
 *******************************************************************************/


import java.util.EmptyStackException;

public class CharacterStack {

  private char[] buffer;
  private int size;

  public CharacterStack() {
    this(16);
  }

  /**
   * @param capacity
   */
  public CharacterStack(int capacity) {
    buffer = new char[capacity];
    size = 0;
  }

  /**
   * @return
   */
  public int size() {
    return size;
  }

  /**
   * @return
   */
  public char peek() {
    final int len = size;
    if (size == 0) {
      throw new EmptyStackException();
    }
    return buffer[len - 1];
  }

  /**
   * @return
   */
  public char pop() {
    int len = size;
    if (len == 0) {
      throw new EmptyStackException();
    }
    --len;
    final char result = buffer[len];
    size = len;
    return result;
  }

  /**
   * @param c
   */
  public void push(char c) {
    if (size == buffer.length) {
      char[] newBuffer = new char[buffer.length * 2 + 1];
      System.arraycopy(buffer, 0, newBuffer, 0, buffer.length);
      buffer = newBuffer;
    }
    buffer[size++] = c;
  }

}