自定义栈和队列

一、栈

首先来使用简单的方式LinkedList来定义

import java.util.LinkedList;/** * Created by lili on 15/11/14. */public class MyStack {    private LinkedList linkedList;    public MyStack() {        linkedList = new LinkedList();    }    public void push(Object o) {        linkedList.addFirst(o);    }    public Object pop() {        //删除并返回        return linkedList.removeFirst();    }    public boolean isEmpty() {        return linkedList.isEmpty();    }}

再使用数组的方式来定义，这个包括了容量的扩充

（1）首先定义一个接口

public interface IStack<T> {      //元素出栈，并返回出栈元素      public T pop();            //元素入栈      public void push(T element);            //获取栈顶元素      public T peek();            //判断栈是否为空      public boolean isEmpty();            public void clear();  }  

（2）再来实现该接口

public class ArrayStack<T> implements IStack<T> {      private final int DEFAULT_SIZE = 3;      private int size = 0;      private int capacity = 0;            //top指向下一个能够添加元素的位置      private int top = 0;      private Object[] array;            public ArrayStack(){          this.capacity = this.DEFAULT_SIZE;          this.array = new Object[this.capacity];          this.size = 0;      }            public ArrayStack(int capacity){          this.capacity = capacity;          this.array = new Object[this.capacity];          this.size = 0;      }            @Override      public boolean isEmpty() {          // TODO Auto-generated method stub          return size == 0;      }        @Override      public T peek() {          // TODO Auto-generated method stub          return (T)this.array[this.top-1];      }        @Override      public T pop() {          // TODO Auto-generated method stub          T element = (T)this.array[top - 1];          this.array[top-1] = null;          this.size--;          return element;      }        @Override      public void push(T element) {          // TODO Auto-generated method stub          if(this.size < this.capacity){              this.array[top] = element;              this.top++;              this.size ++;          }else{  //          System.out.println("out of array");              enlarge();              push(element);          }      }            public void enlarge(){          this.capacity = this.capacity + this.DEFAULT_SIZE;          Object[] newArray = new Object[this.capacity];          System.arraycopy(array, 0, newArray, 0, array.length);          Arrays.fill(array, null);          this.array = newArray;      }            public int size(){          return this.size;      }        @Override      public void clear() {          // TODO Auto-generated method stub          Arrays.fill(array, null);          this.top = 0;          this.size = 0;          this.capacity = this.DEFAULT_SIZE;          this.array = new Object[this.capacity];      }  }  

二、队列

（1）可以使用两个栈的方式来实现队列，如下使用的是LinkedList的方式

public class MyQueue{  private LinkedList list = new LinkedList();  public void clear()//销毁队列  {      list.clear();  }  public boolean QueueEmpty()//判断队列是否为空  {      return list.isEmpty();  }  public void enQueue(Object o)//进队  {      list.addLast(o);  }  public Object deQueue()//出队  {      if(!list.isEmpty())      {          return list.removeFirst();      }      return "队列为空";  }  public int QueueLength()//获取队列长度  {      return list.size();  }  public Object QueuePeek()//查看队首元素  {      return list.getFirst();  }

（2）使用数组的方式来定义队列

public class Queue<E> {      private int front;      private int rear;      private int count;      private int queueSize;      private E[] object;      public Queue() {          this(10);      }      public Queue(int queueSize) {          this.queueSize = queueSize;          this.object = (E[]) new Object[queueSize];          this.front = 0;          this.rear = 0;          this.count = 0;      }      public boolean isEmpty() {          return count == 0;      }      public boolean isFull() {          return count == queueSize;      }      public void push(E o) {          if (this.isFull()) {              throw new RuntimeException("队列是满的");          }          count++;          object[rear] = o;          rear = (rear + 1) % queueSize;      }      public E pop() {          E result;          if (this.isEmpty()) {              throw new RuntimeException("队列是空的");          }          result = this.object[front];          count--;          front = (front + 1) % queueSize;          return result;      }      public E peek() {          if (this.isEmpty()) {              throw new RuntimeException("队列是空的");          }          return this.object[front];      }      public int getCount() {          return count;      }      public int getQueueSize() {          return queueSize;      }      public int getFront() {          return front;      }      public int getRear() {          return rear;      }      public E[] getObject() {          return object;      }  }