Question about creating and using classes.

**iDizzle** · March 24th, 2012, 11:28 PM

Hi everyone. So I have edited this post with another assignment that I'm working on. I am writing a class called bandBooster that contains methods to update candy sales. So my question is how do I use the class that I created below to implement it into another program. When I try to write another program, the method names are not recognized in their. I'm using Eclipse SDK as the compiler and I know it creates a .java and a .class file. Is there something I need to do like open both files in order to use the class in another program or something?

The class that I want to use:

public class bandBooster
{
	private String name;
	private int boxesSold;
 
	public void boosterName(String name)
	{
	boxesSold=0;
	}
 
	public String getName()
	{
		return name;
	}
 
	public int updateSales(int sold)
	{
		boxesSold=boxesSold+sold;
		return boxesSold;
	}
	public String toString()
	{
		return name + ":" + boxesSold + "boxes";	
	}
 
}

This is the program that I want to use the methods from the above class in:

import java.util.Scanner;
public class boosterSales
{
	public static void main(String[] args) 
	{	
		name name1=new name(Joe);
		name name2=new name(Bob);
 
		boxesSold sold1=new sold2;
		boxesSold sold2=new sold2;
 
 
		Scanner scan=new Scanner(System.in);
		System.out.println("How many boxes did Joe sell this week?");
		sold1=scan.nextInt();
 
		name1.updateSales(boxesSold);
 
		System.out.println("This week Joe sold; " + boxesSold);
 
	}
 
}

**Norm** · March 25th, 2012, 07:24 AM

So how would I use this class to write a separate program?

To make a program from a class, add a main() method to it. The main() method will have to create an instance of the class and call its methods as needed.

Please Edit your post and wrap your code with[code=java]<YOUR CODE HERE>[/code] to get highlighting

**iDizzle** · March 25th, 2012, 05:39 PM

Originally Posted by Norm

To make a program from a class, add a main() method to it. The main() method will have to create an instance of the class and call its methods as needed.

Please Edit your post and wrap your code with[code=java]<YOUR CODE HERE>[/code] to get highlighting

Ah, thank you! That looks much better. So to add a main I would add it below all of that code above? What did you mean by the main() will create an instance of the class? Sorry, I'm a beginner beginner. =/

**Norm** · March 25th, 2012, 05:56 PM

You create an instance of a class by using a new statement:
new TheClassName();

What do you want or expect the class to do when you execute it?

**iDizzle** · March 30th, 2012, 06:18 PM

Hi guys. So I updated the first post with more of what I'm trying to do. For an assignment I need to create a class and write another program using methods from that class. When I try to use them method names they are unrecognized and don't work. Any info would be greatly appreciated. Thanks!

**Norm** · March 30th, 2012, 06:25 PM

try to use them method names they are unrecognized

That sounds like a compiler error. Please copy and paste here the full text of the error messages.

**iDizzle** · March 30th, 2012, 06:42 PM

This is the error that I get.

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
name cannot be resolved to a type
name cannot be resolved to a type
Duplicate local variable name1
name cannot be resolved to a type
Joe cannot be resolved to a variable
name cannot be resolved to a type
Duplicate local variable name2
name cannot be resolved to a type
Bob cannot be resolved to a variable
boxesSold cannot be resolved to a type
Syntax error on token "new", delete this token
sold2 cannot be resolved to a variable
boxesSold cannot be resolved to a type
Syntax error on token "new", delete this token
boxesSold cannot be resolved to a variable
boxesSold cannot be resolved to a variable

at boosterSales.main(boosterSales.java:17)

**iDizzle** · March 30th, 2012, 06:50 PM

This is the error that I get.

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
name cannot be resolved to a type
name cannot be resolved to a type
Duplicate local variable name1
name cannot be resolved to a type
Joe cannot be resolved to a variable
name cannot be resolved to a type
Duplicate local variable name2
name cannot be resolved to a type
Bob cannot be resolved to a variable
boxesSold cannot be resolved to a type
Syntax error on token "new", delete this token
sold2 cannot be resolved to a variable
boxesSold cannot be resolved to a type
Syntax error on token "new", delete this token
boxesSold cannot be resolved to a variable
boxesSold cannot be resolved to a variable

at boosterSales.main(boosterSales.java:17)

**Norm** · March 30th, 2012, 06:56 PM

Those are not compiler error messages. They are generated by the IDE. Those messages are missing a lot of information about the errors. The IDE must give you some visual indication of the error in the source. I can't see that indication. Pick one message and try to change the program to fix it. For example where is name defined?

Here is what a compiler error message looks like:

TestSorts.java:138: cannot find symbol
symbol  : variable var
location: class TestSorts
         var = 2;
         ^

Notice it has the source line number, the source line, a ^ under the location of the error and a message describing the error.

Use the javac command to get useful error messages.

**iDizzle** · March 30th, 2012, 07:09 PM

My compiler has little "x"s at the beginning of the line to annotate errors and for example, line 6 says;
----------------------------------------------------------------------
Joe cannot be resolved to a variable
name cannot be resolved to a type
name cannot be resolved to a type
Duplicate local variable name1
name1 cannot be resolved to a type
----------------------------------------------------------------------
So to me it looks like the variables that were declared in the class are not being recognized when I try to use them

**Norm** · March 30th, 2012, 07:10 PM

Sorry I can not see the 'x's from your IDE (not compiler)
Use the javac command to get the compiler error messages.

**iDizzle** · March 31st, 2012, 03:40 AM

Sorry, how do I use the java command? I'm a beginner =[

**Norm** · March 31st, 2012, 06:36 AM

open a command prompt window, use the change directory (CD) command to change to the directory with the source file: (.java) and enter the command:
javac <THESOURCEFILENAMEHERE>.java

If the javac command is not found by the OS, it will give a message.

**iDizzle** · April 1st, 2012, 12:40 PM

So I guess my question is, in order to use the methods and variables from a class(bandBooster) that I've created, in the new program(boosterSales) do I have to open both files at the same time? Or do I need to import the bandBooster class into the boosterSales program some how? Or do I need to put the main of the boosterSales program directly below the bandBooster class? I think the compiler program that I'm using to do this is just seeing the bandBooster class and the boosterSales program as standalone programs.

**Norm** · April 1st, 2012, 12:47 PM

in order to use

The javac command must be able to find definitions for the classes that you use in a java source file when it is compiling that source file. The definition files for the classes should be on the classpath for the javac command.
If all the class definitions are in the same folder the javac command should be able to find them.
If any of the classes are in packages then the classpath must point to the folder that holds the package folder.

**iDizzle** · April 1st, 2012, 01:04 PM

ohh ok. Well, both of the files are in the same folder. They are both in the "bin" folder and both in the "src" folder.

**Norm** · April 1st, 2012, 01:07 PM

Can you post the full text of the compiler's error messages?

**iDizzle** · April 1st, 2012, 02:04 PM

As far as I know, these are the error messages that it's giving me. These error messages are from the boosterSales program that I'm trying to use the bandBooster class methods and variables from. No errors in the bandBooster class. But only in the boosterSales program. Both the bandBooster class and the boosterSales program are in the same project.

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
name cannot be resolved to a type
name1 cannot be resolved to a type
Joe cannot be resolved to a variable
name cannot be resolved to a type
name2 cannot be resolved to a type
Bob cannot be resolved to a variable
boxesSold cannot be resolved to a type
Syntax error on token "new", delete this token
boxesSold cannot be resolved to a type
Syntax error on token "new", delete this token
boxesSold cannot be resolved to a variable
boxesSold cannot be resolved to a variable

at boosterSales.main(boosterSales.java:17)

**iDizzle** · April 1st, 2012, 02:05 PM

Sorry, this is all just so confusing to me. My text book is very vague about this. I understand the concept of creating and using a class but I'm just having trouble putting it into use. Thanks for your help, I appreciate it.

**Norm** · April 1st, 2012, 02:14 PM

name cannot be resolved to a type

A type is the name of a class or a primitive like int. By convention class names should start with uppercase letters.
You are using the symbol: name where there should be the name of a class. For example String is the name of a class.

You need to look at your text book to see how to define variables. Your syntax is wrong.

**iDizzle** · April 1st, 2012, 03:14 PM

Will do, thank you! Yeah because I did not know where the problem was coming from. As long as I know its a syntax error than I know where to being. Thanks again! I'll see how it works out afterwards.

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