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2. Java示例
3. 如何实现堆栈？(How to implement stack?)

如何实现堆栈？(How to implement stack?)

问题描述 (Problem Description)

如何实现堆栈？

解决方案 (Solution)

下面的示例演示如何通过创建用户定义的push（）方法来输入元素来实现堆栈，以及pop（）方法从堆栈中检索元素。

public class MyStack {
   private int maxSize;
   private long[] stackArray;
   private int top;
   public MyStack(int s) {
      maxSize = s;
      stackArray = new long[maxSize];
      top = -1;
   }
   public void push(long j) {
      stackArray[++top] = j;
   }
   public long pop() {
      return stackArray[top--];
   }
   public long peek() {
      return stackArray[top];
   }
   public boolean isEmpty() {
      return (top == -1);
   }
   public boolean isFull() {
      return (top == maxSize - 1);
   }
   public static void main(String[] args) {
      MyStack theStack = new MyStack(10); 
      theStack.push(10);
      theStack.push(20);
      theStack.push(30);
      theStack.push(40);
      theStack.push(50);
      while (!theStack.isEmpty()) {
         long value = theStack.pop();
         System.out.print(value);
         System.out.print(" ");
      }
      System.out.println("");
   }
}

结果 (Result)

上面的代码示例将产生以下结果。

50 40 30 20 10

以下是通过创建用户定义的push（）方法来输入元素来实现堆栈的另一个示例，以及用于从堆栈中检索元素的pop（）方法。

import java.util.*;
public class Demo {
   static void showpush(Stack stack1, int a) {
      stack1.push(new Integer(a));
      System.out.println("push(" + a + ")");
      System.out.println("stack: " + stack1);
   } 
   static void showpop(Stack stack1) {
      Integer a = (Integer) stack1.pop();
      System.out.println(a);
      System.out.println("stack: " + stack1);
   } 
   public static void main(String args[]) {
      Stack stack1 = new Stack();
      System.out.println("stack: " + stack1);
      showpush(stack1, 40);
      showpush(stack1, 50);
      showpush(stack1, 60);
      showpop(stack1);
      showpop(stack1);
      showpop(stack1);
      try {
         showpop(stack1);
      } catch (EmptyStackException e) {
         System.out.println("it Is Empty Stack");
      } 
   }
}

上面的代码示例将产生以下结果。

stack: []
push(40)
stack: [40]
push(50)
stack: [40, 50]
push(60)
stack: [40, 50, 60]
60
stack: [40, 50]
50
stack: [40]
40
stack: []
it Is Empty Stack