java的一些程序

1、文件读取并打印

import java.io.*;
public class readandprint{
//*********Found********
public static void main(String args[]) throws Exception{
long filePoint = 0 ;
String s;
RandomAccessFile file = new RandomAccessFile("D:\\javaceshu\\readandprint.java","r");
long fileLength = file.length();
while (filePoint<fileLength){
//*********Found********
s = file.readLine();
System.out.println(s); 
filePoint = file.getFilePointer();
                            }
file.close();
    }
}

2、图形程序显示乘法

import javax.swing.JOptionPane;
public class Java_1 {
public static void main( String args[] ) {
int x, y, result;
String xVal, yVal;
xVal = JOptionPane.showInputDialog( "输入第1个整数:" );
yVal = JOptionPane.showInputDialog( "输入第2个整数:" );
//*********Found********
x = Integer.parseInt(xVal);
y = Integer.parseInt( yVal );
result = x * y;
//*********Found********
JOptionPane.showMessageDialog( null, "两个数的积: " + result );
System.exit( 0 );
}
}

3、从命令行参数输入 java_24_3 7 （先编译完后）会显示7的阶乘是5040

public class _24_3{
public static void main(String[] args){
String num;
if(args.length > 0)
//*********Found********
num =args[0];
else
num = "5";
//*********Found********
int input = Integer.parseInt(num);
int result = Java_3(input);
System.out.println(input+ " 的阶乘是 "+ result);
}
public static int Java_3(int x)
{
if( x < 0 )
return 0;
int fact = 1;
while(x > 1)
{
//*********Found********
fact = fact * x;
x = x-1;
}
return fact;
}
}