Beginner Java Problem

Question

DARK_BYTE 0 Junior Poster in Training

14 Years Ago

Hi wat's wrong with my "do while" loop it never allows me to enter the grade even if I enter 'A' or 'B' or 'C'..?

import java.util.Scanner;
public class ArraysOfStudentDetails {
	public static void main( String [] args )
	{
		Scanner in = new Scanner( System.in );
		final int SIZE = 10;
		String[] names = new String[SIZE];
		char[] module1 = new char[SIZE];
		char[] module2 = new char[SIZE];
		char[] module3 = new char[SIZE];
		char[] module4 = new char[SIZE];
		char[] module5 = new char[SIZE];
		int j;
		char grade;
		String holding;
		for( int i = 0; i < SIZE; i ++)
		{
			j = i + 1;
			System.out.println( "Please enter student #" + j + 
					" details:");
			System.out.print( "Enter name for student #" + j );
			names[i] = in.nextLine();
			do
			{
				System.out.print( "Enter grade #1" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' || grade != 'B' || grade != 'C'
				|| grade != 'D' || grade != 'E' );
			module1[i] = grade;
			
			do
			{
				System.out.print( "Enter grade #2" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' || grade != 'B' || grade != 'C'
				|| grade != 'D' || grade != 'E' );
			module2[i] = grade;
			
			
			do
			{
				System.out.print( "Enter grade #3" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' || grade != 'B' || grade != 'C'
				|| grade != 'D' || grade != 'E' );
			module3[i] = grade;
			
			
			do
			{
				System.out.print( "Enter grade #4" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' || grade != 'B' || grade != 'C'
				|| grade != 'D' || grade != 'E' );
			module4[i] = grade;
			
			
			do
			{
				System.out.print( "Enter grade #5" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' || grade != 'B' || grade != 'C'
				|| grade != 'D' || grade != 'E' );
			module5[i] = grade;
					
			System.out.println();
			System.out.println();
		
		}
			
			
	}
			
		

}

java

Edited 14 Years Ago by DARK_BYTE because: n/a

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Latest Post 14 Years Ago Latest Post by Jocamps

All 9 Replies

Jocamps 14 Junior Poster

14 Years Ago

It should be AND (&&) statements right instead of OR?

Grn Xtrm 84 Posting Pro in Training

14 Years Ago

Maybe I am misunderstanding the point of the program, but your while is set up with NOT EQUALs. So, while the grade is not equal to A,B,C..... you will enter grades in the do part. If you enter A,B,C... then you won't be fulfilling the condition in the while and you won't re-enter the do part. Not sure if that's what your looking for, but I hope it helps.

peter_budo 2,532 Code tags enforcer

14 Years Ago

It should be AND (&&) statements right instead of OR?

Nope, problem is with the use of "!=" which is basically same as using method "equals()" which is only allowed/available on object type. Character is primitive type hence the error which pop up.
Solution is to use compareTo() method. With simple creation of our own compare method we can get "true" or "false" return that can be used in while loop

public boolean compareChars(Character read, Character grade) {    
    return (read.compareTo(grade) == 0);  
}

Edited 14 Years Ago by peter_budo because: typo

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DARK_BYTE 0 Junior Poster in Training · Answer 1 · 2009-10-12T02:29:05+00:00

DARK_BYTE 0 Junior Poster in Training

14 Years Ago

Actually you people are right it should have been &&; ahhh I am messing up!

Edited 14 Years Ago by DARK_BYTE because: n/a

DARK_BYTE 0 Junior Poster in Training · Answer 2 · 2009-10-12T02:30:47+00:00

Nope, problem is with use of "!=" which is basically as using of "equals()" method which is only allowed on object type. Character is primitive type hence the error which pop up.
Solution is use of compareTo() method. With simple creation of our own compare method we can get "true" or "false" return that can be used in while loop
public boolean compareChars(Character read, Character grade) {    
    return (read.compareTo(grade) == 0);  
}

Thanks but no thanks :P

peter_budo 2,532 Code tags enforcer Team Colleague Featured Poster · Answer 3 · 2009-10-12T02:33:42+00:00

PS: Do not forget to use keyword "static" when adding the above method to your program.

DARK_BYTE 0 Junior Poster in Training · Answer 4 · 2009-10-12T02:50:23+00:00

Nope, problem is with the use of "!=" which is basically same as using method "equals()" which is only allowed/available on object type. Character is primitive type hence the error which pop up.
Solution is to use compareTo() method. With simple creation of our own compare method we can get "true" or "false" return that can be used in while loop
public boolean compareChars(Character read, Character grade) {    
    return (read.compareTo(grade) == 0);  
}

Actually the problem was indeed the || instead of &&;
this works

import java.util.Scanner;
public class ArraysOfStudentDetails {
	public static void main( String [] args )
	{
	
		Scanner in = new Scanner( System.in );
		final int SIZE = 10;
		String[] names = new String[SIZE];
		char[] module1 = new char[SIZE];
		char[] module2 = new char[SIZE];
		char[] module3 = new char[SIZE];
		char[] module4 = new char[SIZE];
		char[] module5 = new char[SIZE];
		int j;
		char grade;
		String holding;
		for( int i = 0; i < SIZE; i ++)
		{			
			j = i + 1;
			System.out.println( "Please enter student #" + j + 
					" details:");
			System.out.print( "Enter name for student #" + j );
			names[i] = in.nextLine();
			do
			{
				System.out.print( "Enter grade #1" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' && grade != 'B' && grade != 'C'
				&& grade != 'D' && grade != 'E' );
			module1[i] = grade;
			
			do
			{
				System.out.print( "Enter grade #2" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' && grade != 'B' && grade != 'C'
				&& grade != 'D' && grade != 'E' );
			module2[i] = grade;
			
			
			do
			{
				System.out.print( "Enter grade #3" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' && grade != 'B' && grade != 'C'
				|| grade != 'D' && grade != 'E' );
			module3[i] = grade;
			
			
			do
			{
				System.out.print( "Enter grade #4" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' && grade != 'B' && grade != 'C'
				&& grade != 'D' && grade != 'E' );
			module4[i] = grade;
			
			
			do
			{
				System.out.print( "Enter grade #5" );
				holding = in.nextLine();
				grade = holding.charAt(0);
			}
			while( grade != 'A' && grade != 'B' && grade != 'C'
				&& grade != 'D' && grade != 'E' );
			module5[i] = grade;
					
			System.out.println();
			System.out.println();
		
		}
			
			
	}
			
		

}

Thanks a lot everyone

peter_budo 2,532 Code tags enforcer Team Colleague Featured Poster · Answer 5 · 2009-10-12T03:26:27+00:00

peter_budo 2,532 Code tags enforcer

14 Years Ago

LOL, seriously I need holidays...

Jocamps 14 Junior Poster · Answer 6 · 2009-10-12T09:46:37+00:00

Actually the problem was indeed the || instead of &&;
Thanks a lot everyone

told 'ya ;)

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