Thread: I am a java newb and I am having a problem with my while loops.

I have been teaching myself java for fun. I found a site that gives assignments so I have been trying to teach myself by completing the programs assigned by the site. This assignment asked that I write a program asking the user to guess a random number. Anyways, this is like my 3rd day of teaching myself this stuff so I am basically feeling it out as I go. Can anybody tell me how to fix this? Or, perhaps more importantly, why this doesn't work? Any help would be appreciated.


Thanks!!!

The errors the program is giving me are all in the underlined line. They are:
-Syntax error on token 'while' delete this token.
-Syntax error on token 'boolean' delete


Things I have tried:
-I tried defining the booleans outside of the while loop.
-I tried writing in public static void main whatever (I don't fully understand what that code does yet but it semeed to impact the way the boolean instances interacted.)

Here is the code:

import java.io.*;
public class pickanumber {
 
 
	int x = (int) ((Math.random()*10)+1)
 
 while [boolean rightguess1 = false];
 
{	
 
	try {
 
 
	Reader instream = null;
	BufferedReader userguess = new BufferedReader (instream);
 
	System.out.println("Pick a whole number between 1 and 10");
	String usguess = userguess.readLine();
	int uguess1 = Integer.parseInt(usguess);
 
	if (!(uguess1==x)) {
	System.out.println("Try again");
	boolean rightguess1 = false;
 
	}
	else {
		boolean rightguess1 = true;
	}}
	catch (IOException err) {
		System.out.println("Only whole numbers please");
	}
	System.out.println("Nice job.  The number was " + x);
 
}
	}

Well, I did just figure out that if I remove the word boolean from the code inside of the while loop it connects the boolean at the top of the while loop to the booleans inside of the loop. The problem; however, remain unsolved.

I will re-post next time. I did post the errors. They were:

The errors the program is giving me are all in the underlined line. They are:
-Syntax error on token 'while' delete this token.
-Syntax error on token 'boolean' delete


Can you point me to a good resource regarding methods? It sounds like I misunderstood something basic somewhere.

Thanks!!!

Here is the latest version of my code.

 
import java.io.*;
public class pickanumber {
 
 
	int x = (int) ((Math.random()*10)+1)
  while [boolean rightguess1 = false];
 
{	
 
	try {
 
 
	Reader instream = null;
	BufferedReader userguess = new BufferedReader (instream);
 
	System.out.println("Pick a whole number between 1 and 10");
	String usguess = userguess.readLine();
	int uguess1 = Integer.parseInt(usguess);
 
	if (!(uguess1==x)) {
	System.out.println("Try again");
	 rightguess1 = false;
 
	}
	else {
		break;
	}}
	catch (IOException err) {
		System.out.println("Only whole numbers please");
	}
	System.out.println("Nice job.  The number was " + x);
 
}
	}

I re-wrote my code but now I have a new error.

Exception in thread "main" java.lang.NoSuchMethodError: main


Here is my new code. Hopefully it will be easier to read:



import java.io.*;
//imports whatever I need for the buffer reader (not sure how that works yet)

public class pickanumber {
//declares class

public void guessnum (boolean[] args) {

int x = (int) ((Math.random()*10)+1);

boolean whiletest = false;
while (whiletest = false) {
//declares whiletest to be false and begins a loop contingent upon that.
//Making whiletest true ends the loop.

System.out.println("Pick a whole number between 1 and 10");

BufferedReader ubuff = new BufferedReader(new InputStreamReader(System.in));
try {
String usguess = ubuff.readLine();
int i = Integer.parseInt(usguess);
if (i==x) {
System.out.println("Nice job the number was " + x);
whiletest = true;
}

else {
System.out.println("Sorry, try again");
whiletest = false;
}
}


catch (IOException ioe) {
System.out.println("User input not valid.");
System.out.println("All your base are belong to me.");
}
}



}

}

I have a new error.

Exception in thread "main" java.lang.NoSuchMethodError: main

Can you explain what you did to get this error message. Is it when you tried to execute your program?
What command did you execute?

The java command requires that the class you pass to it have a special method: main coded as:
public static void main(String[] args) {
// put code here to start the class going
} // end main()

Yes. That's how I got the error message.

Thanks for the tip. I finally got past the compiler. Now I can run the program, but when it runs it says program terminated. Also, there is an error on line 11 of my code. It gets past the compiler but it says "local variable whiletest is never read." I am very confused. My whole loop is built on that boolean so it is utilized. I guess I am not sure what read means. As far as I can tell the logic should work. Where am I going wrong? Here is my new code.



import java.io.*;
//imports whatever I need for the buffer reader (not sure how that works yet)

public class pickanumber {
//declares class

public static void main(String[] args) {
int x = (int) ((Math.random()*10)+1);

boolean whiletest = false;
while (whiletest = false) {
//declares whiletest to be false and begins a loop contingent upon that.
//Making whiletest true ends the loop.

System.out.println("Pick a whole number between 1 and 10");

InputStreamReader istream = new InputStreamReader(System.in);
BufferedReader ubuff = new BufferedReader (istream);
try {
String usguess = ubuff.readLine();
int i = Integer.parseInt(usguess);
if (i==x) {
System.out.println("Nice job the number was " + x);
whiletest = true;
}

else {
System.out.println("Sorry, try again");
whiletest = false;
}
}


catch (IOException ioe) {
System.out.println("User input not valid.");
System.out.println("All your base are belong to me.");
}
}



}

}

Please copy and paste the full text of the error message here.
Also please wrap your posted code in code tags to preserve formatting.
See: BB Code List - Java Forums

while (whiletest = false) {
This is an assignment statement not a comparison

Hah I can't believe it was that simple. Thanks Norm! I fixed it. I did give you the full error message that eclipse gave me. That's all it said when I clicked on the little error icon.

Here is the final code:


import java.io.*;
//imports whatever I need for the buffer reader (not sure how that works yet)

public class pickanumber {
//declares class

public static void main(String[] args) {
int x = (int) ((Math.random()*10)+1);

boolean whiletest = false;
while (whiletest == false) {
//declares whiletest to be false and begins a loop contingent upon that.
//Making whiletest true ends the loop.

System.out.println("Pick a whole number between 1 and 10");

InputStreamReader istream = new InputStreamReader(System.in);
BufferedReader ubuff = new BufferedReader (istream);
try {
String usguess = ubuff.readLine();
int i = Integer.parseInt(usguess);
if (i==x) {
System.out.println("Nice job the number was " + x);
whiletest = true;
}

else {
System.out.println("Sorry, try again");
whiletest = false;
}
}


catch (IOException ioe) {
System.out.println("User input not valid.");
System.out.println("All your base are belong to me.");
}
}



}

}

Thanks for the tips. I will play with those to see if I can get my program working that way as well. Also, I found that I did still have an error. The catch (method?) whatever the term for that is was not working. I did some research and found out why. Here is the new completely and fully functional code.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class picknumadvanced {
	//declares class
 
public static void main(String[] args) { 	
int x = (int) ((Math.random()*10)+1);
 
boolean whiletest = false;
while (whiletest  == false) {
	//declares whiletest to be false and begins a loop contingent upon that.
	//Making whiletest true ends the loop.
 
	System.out.println("Pick a whole number between 1 and 10");
 
    InputStreamReader istream = new InputStreamReader(System.in);
    BufferedReader ubuff = new BufferedReader (istream);
    	try {
    		String usguess = ubuff.readLine();
    		int i = Integer.parseInt(usguess);		
    	 	if (i==x) {
    			System.out.println("Nice job the number was " + x);
    			whiletest = true;
    			 }
 
    	 	else {
    			System.out.println("Sorry, try again");
    			whiletest = false;
    			 }	   
    	    }
 
 
    	catch (NumberFormatException nfe) {
    		System.out.println("User input not valid.");
    		System.out.println("All your base are belong to me.");
 
    	}
    	catch (IOException ioe) {
    		System.out.println("You suck");
    	}
}
 
 
 
}
 
}

InputStreamReader istream = new InputStreamReader(System.in);
BufferedReader ubuff = new BufferedReader (istream);
These could be outside the loop. No need to create them every time you loop

Here is the more refined version based on your reccomendations Norm. They let me remove a few lines of code.

Thanks for all the help!

On to the next challenge.

 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class picknumadvanced {
	//declares class
 
public static void main(String[] args) { 	
int x = (int) ((Math.random()*10)+1);
 
boolean whiletest = true;
while (whiletest) {
	//declares whiletest to be false and begins a loop contingent upon that.
	//Making whiletest true ends the loop.
 
	System.out.println("Pick a whole number between 1 and 10");
 
    InputStreamReader istream = new InputStreamReader(System.in);
    BufferedReader ubuff = new BufferedReader (istream);
    	try {
    		String usguess = ubuff.readLine();
    		int i = Integer.parseInt(usguess);		
    	 	if (i==x) {
    			System.out.println("Nice job the number was " + x);
    			whiletest = false;
    			 }
 
    	 	else {
    			System.out.println("Sorry, try again");
 
    			 }	   
    	    }
 
 
    	catch (NumberFormatException nfe) {
    		System.out.println("User input not valid.");
    		System.out.println("All your base are belong to me.");
 
    	}
    	catch (IOException ioe) {
    		System.out.println("You suck");
    	}
}
 
 
 
}
 
}

Originally Posted by Norm

InputStreamReader istream = new InputStreamReader(System.in);
BufferedReader ubuff = new BufferedReader (istream);
These could be outside the loop. No need to create them every time you loop

Ok so once I create the buffreader I only need to reference it via string inside of the loop?

Err, to amend that statement... well. How exactly does the buffreader work?

Also what sort of error would trigger this catch statement?
catch (IOException ioe) {
System.out.println("You suck");
}

Java required that I have an input output exception like this but I can't figure out what type of error would trigger it.

Do a Google. Anytime you try to read something it is possible for there to be something going wrong and throwing an exception.