example11_4.java

书中的例题

  /* 堆栈演示 */
  import java.awt.*;
  import java.awt.event.*;
  import java.util.*;
  class StackApp extends Frame implements ActionListener 
  {
   Button btnNew,btnPush,btnPop; 
   TextField txt0;
   Panel p1,p2;
   TextField txt[]=new TextField[7];
   Stack theStack=new Stack();
   int i=1,k=0;
   String s[]=new String[7];

  StackApp()
   {
	super("** 堆栈演示 **");
	setSize(400,200);
	show();
    btnNew=new Button("建立堆栈");
	btnPush=new Button("Push（入栈）");
	btnPop=new Button("Pop（出栈）");
	txt0=new TextField(10);
	btnNew.addActionListener(this);
	btnPush.addActionListener(this);
	btnPop.addActionListener(this);
    setLayout(new BorderLayout());
	p1=new Panel();
	p2=new Panel();
   	add(p1,BorderLayout.NORTH);
	add(p2,BorderLayout.CENTER);
	p1.setLayout(new FlowLayout());
	p1.add(btnNew);
    p1.add(btnPush);
    p1.add(btnPop);
    p1.add(txt0);
	btnPush.enable(false);
	btnPop.enable(false);
    p2.setLayout(new GridLayout(6,3));
	for (i=6; i>=1; i--)
   	  {
		txt[i]=new TextField(10);
        p2.add(new Label());
		p2.add(txt[i]);
        p2.add(new Label());

	  }
    validate();
   }
  public void actionPerformed(ActionEvent e)
	{
      if (e.getSource()==btnNew)
		{ 		
         s[1]="思维论坛";
		 s[2]="Java爱好者";
		 s[3]="百度";
		 for (i=1; i<=3; i++)
		 {
           theStack.push(s[i]);
           txt[i].setText(s[i]);
		   k=k+1;
		 }
		 btnPush.enable(true);
         btnPop.enable(true);
		}
	  else  if (e.getSource()==btnPush)
		{ 		
		   if (txt0.getText()!=null)
		   {
			   k++;			   
			   s[k]=txt0.getText();
			   theStack.push(s[k]);
			   txt[k].setText(s[k]);
			}
		}
      else if (e.getSource()==btnPop)
        {
		   if (!theStack.empty())
            {
			  txt0.setText(s[k]);         	  
			  s[k]="";
			  theStack.pop();
		      txt[k].setText(s[k]);
			  k--;
            }
           else 
		 	{ 
		 	  txt0.setText("堆栈是空的"); 
		    }
        }
	}
 }

 public class Example11_4
  {
	public static void main(String[] args) 
	{
		new StackApp();
	}
  }