Thread: NumberFormatException

I’m doing this exercise where I need to design a program that will generate a random number between 1 and 100 and then let the user guess the number and tell them whether the guess is too high or too low. Here’s the code:

The Evaluator class:

import java.io.*;
 
public class Evaluator
{
    private KeyboardReader reader = new KeyboardReader();
 
	public String evaluate(int guess, int secretNum)
	{   
	    if(guess > secretNum)
		   return "Too high";
		else 
		   return "Too low";
	} // evaluate()
 
	public void run()
	{
	    int secretNum = 1 + (int)(Math.random()*100);
		reader.prompt("What's your guess? -> ");
		guess = reader.getKbInt();
		reader.display(evaluate(guess, secretNum));
	} // run()
 
	public static void main(String args[])
	{   
	    Evaluator app = new Evaluator();
		app.run();
	} // main
}

The KeyboardReader class

import java.io.*;
 
public class KeyboardReader
{
 
	private BufferedReader reader;
 
	public KeyboardReader()
	{
	    reader = new BufferedReader(new InputStreamReader(System.in));
    }  // KeyboardReader
 
    private String readKeyboard()
	{
	    String line = "";
		try
		{   reader.readLine();   }
		catch (IOException e)
		{   e.printStackTrace(); }
		return line; 
	} // readKeyboard()
 
	public String getKbInput()
	{   return readKeyboard();
	}
 
	public int getKbInt()
	{   return Integer.parseInt(readKeyboard());
	}
 
	public double getKbDouble()
	{   return Double.parseDouble(readKeyboard());
	}
 
	public void prompt(String s)
	{   System.out.print(s); 
	}
 
	public void display(String s)
	{   System.out.print(s);
	}
} // KeyboardReader

I entered an integer and a NumberFormatException was thrown:

C:\LearnJava>java Evaluator
What's your guess? -> 4
Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.base/java.lang.NumberFormatException.forInputString(Num berFormatException.java:68)
at java.base/java.lang.Integer.parseInt(Integer.java:668)
at java.base/java.lang.Integer.parseInt(Integer.java:776)
at KeyboardReader.getKbInt(KeyboardReader.java:28)
at Evaluator.run(Evaluator.java:21)
at Evaluator.main(Evaluator.java:28)

How do I fix this?

Here’s the code:

Please copy and paste here the code wrapped in code tags.

a NumberFormatException was thrown:

Also copy the full text of the error message and paste it here.

Don't post images. Text can not be copied from an image to include in the response.

Great