randomdemo.java

Java面向对象编程(随书配套源代码) 阐述了面向对象编程的思想

package chapter13;
import java.io.*;
public class RandomDemo
{
	public static void main(String args[]) throws IOException
	{
		int lineNo;
		long fp;
		InputStreamReader stdin=new InputStreamReader(System.in);
		BufferedReader bufin=new  BufferedReader(stdin);
		RandomAccessFile file=new RandomAccessFile("random.txt","rw");
		System.out.println("请输入6个字符串：\n");
		int len[]=new int[6];
		String strInput[]=new String[6];
		for(int i=0;i<6;i++)
		{
			System.out.print("行号"+(i+1)+":");
			strInput[i]=bufin.readLine();
			len[i]=strInput[i].length();
			file.write((strInput[i]+"\n").getBytes());
		}
		while(true) 
		{
			fp=0;
			file.seek(0);
			System.out.print("你要显示第几行？"+"(1--6) ");
			lineNo=Integer.parseInt(bufin.readLine());
			for(int i=1;i<lineNo;i++)
            	fp=fp+(long)len[i-1]+1;
		    file.seek(fp);
			System.out.println("第"+lineNo+"行"+":"+file.readLine());
			System.out.println("继续吗?"+"(y/n)");
			if((bufin.readLine().equals("n"))) 
			   break;
		}
		file.close();
	}
}