ch3_e3_17.java

代码包括《Java语言与面向对象程序设计题解与实验指导》一书中 “习题解答”部分的所有程序的Java源代码和编译后生成的字节码或相应的HTML文件。 盘中的目录与书中的章节一致。

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

public class ch3_e3_17 extends Applet implements ActionListener
{
	Label prompt;
	TextField input;
	TextArea result;
	Button btn;
	long value;
	int count;
	String resultString = "这个数的所有素数因子为 \n";

	public void init()
	{						  
		prompt = new Label("请输入欲求素数因子的正整数：");
		input = new TextField(5);
		result = new TextArea(8,30);
		btn = new Button("输出");
		add(prompt);
		add(input);
		add(btn);
		add(result);
		btn.addActionListener(this);
	}

	public void actionPerformed(ActionEvent e)
	{
 	  try
 	  {
		value = Long.parseLong(input.getText());
                count=0 ;
		if( value%2 == 0)
		{
		  resultString = resultString + "2\t";
		  count++;
		  value /= 2;
		}
		if( value%3 == 0)
		{
		  resultString = resultString + "3\t";
		  count++;
		  value /= 3;
		}
		for (int i=5; i<=value; i+=2)
		{
		  if( value%i != 0)
			continue;
		  else
		  {
			boolean flag = true;

			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);
			    if ( ++count <4 )
				resultString = resultString + "\t";
			    else
			    {
				count = 0;
				resultString = resultString + "\n";
			    }
			} // if(flag)
			value /= i;
		  }// else
		}// for(i)
		result.setText(resultString);
		resultString = "这个数的所有素数因子为 \n";
	  }
	  catch(NumberFormatException nfe)
	  {
		result.setText("格式错误，请输入正整数。");
	  }

	}// end of actionPerformed() method

} // end of class