ch3_e3_16.java

各种关于JAVA的初级编程

import java.applet.*;
import java.awt.*;
import java.awt.event.*;

public class ch3_e3_16 extends Applet implements ActionListener
{
    Label prompt;
    TextField ceiling,floor;
    TextArea result;
    Button btn;
    int max=0,min=0,temp=0;
    String resultString = "这个范围内的素数为 \n";

    public void init()
    {                         
        prompt = new Label("请输入欲列出素数的上下限范围：");
        ceiling = new TextField(5);
        floor = new TextField(5);
        result = new TextArea(8,30);
        btn = new Button("输出");
        add(prompt);
        add(ceiling);
        add(floor);
        add(btn);
        add(result);
        btn.addActionListener(this);
    }

    public void actionPerformed(ActionEvent e)
    {
      try
      {
        max = Integer.parseInt(ceiling.getText());
        min = Integer.parseInt(floor.getText());
        if( max < min )
        {
          temp = max;
          max = min;
          min = temp;
        }  
        for (int i=min; i<=max; i++)
        {
            boolean flag = true;

            if ( i==2 || i==3 )
            {
                resultString = resultString
                  + Integer.toString(i) + "\n";
                continue;
            }
            if ( i%2 ==0 )
              continue;
            else
              for(int j=3; j<i; j+=2)
              {
                if( i%j == 0 ) 
                {  flag = false;
                   break;   }
              }

            if(flag)
                resultString = resultString 
                  + Integer.toString(i) + "\n";
        }// for(i)
        result.setText(resultString);
        resultString = "这个范围内的素数为 \n";
      }
      catch(NumberFormatException nfe)
      {
        result.setText("格式错误，请输入正整数。");
      }

    }// end of actionPerformed() method

} // end of class