如何显示文本文件中的随机行？

Question

I am new to Java and stackoverflow. I have a text file that I wish for my Java program to read and then pick a random line and display it. What I've found only demonstrates bytes and characters. How can I use strings or just a line? I apologize that this question has been asked before, but other posts have not helped me. I'm at a loss and I feel like there's a simple solution for this.

Here's what I have so far:

package Nickname;

import java.util.Scanner;
import java.io.*;

public class Nickname {

    public static void main(String[] args) throws IOException {

        RandomAccessFile randomFile = new RandomAccessFile("names.txt", "r");

    }

}

Answer 1

I suggest you use a buffered reader. With in.readLine() you can get your next line from the file.

Math.random() generated a (pseudo) random number between 0 and 1. By multiplying and casting to int you generate a number between 0 and 100. If that random number happens to be of a specific value (50 in this case) you stop your loop and print the line.

You can change the odds of the loop breaking by changing the multiplication factor to anything you like. Just make sure to compare to a number in your specified range.

BufferedReader in = new BufferedReader(new FileReader(file));

while (in.ready()) {

  String s = in.readLine();

  //1% chance to trigger, if it is never triggered by chance you will display the last line
  if (((int)(Math.random*100)) == 50) 
     break;

}
in.close();
System.out.println(s);

Alternatively a solution like this might be more elegant and gives you an evenly distributed chance of getting either of the values:

BufferedReader in = new BufferedReader(new FileReader(file));
List<String> myNicknames = new ArrayList<String>();
String line;

while ( (line = in.readLine()) != null) {
   myNicknames.add(line);
}
in.close();

System.out.println(myNicknames.get( (int)(Math.random() * myNicknames.size()) ));