NulPointerException wont go away

[javano0b]

This program is a currency converter there are two files the foreign.java does all the calculations and asks the questions and what not. That part works fine but now i have to is when the person decides they are done the program has to ask if they want a summary report and then if they do have it print out the conversion dollars and amount.

import java.util.Scanner;
import java.text.NumberFormat;

public class lab9

{
	public static void main( String [] args)
	{
		
		//foreign exchange;//
		final int Max = 20;
		foreign[] exchange = new foreign[Max];
		Scanner scan = new Scanner (System.in);
		String another = "Y";
		int c=0;
		
		
		do
		{
			foreign.titles();
			
			foreign.menu();
			//static methods called before the object is initiated

			
			
			//allows us to call the other methods
		
			exchange[c].getchoice();
			
			
			if (c != 0)
			{	
		
				exchange[c]= new foreign();				
				
				exchange[c].dollars();
				
				exchange[c].calculate();
		
				exchange[c].value();
			
				System.out.println(exchange);
			
				//above call methods from the other class
			}
			
		}
		while (c != 0);
		//tells the program to continue calculating as long as 0 is not selected

		System.out.println("display a summary report? Y/N");
		another = scan.nextLine();
		System.out.print("\nItemt\t\tConversion\t\t\tDollars\t\t\tAmount");
    	for (int i=0; i<c; i++)
			System.out.println(exchange[i]);
		foreign.displaycount();	
		//this static method is only called when the choice is 0 which is the end of the program 
			
	}

}

I know there are things that are missing I took some stuff out to get it so there were no more errors but now i get the NullPointerException and I dont know what to do any ideas? Also i didnt include the foreign.java that is being called because i havent made any changes to that.

[j2me64]

if you want make a call to getchoice() in line 29 the element exchange[c] must exist. i can't see any initialization for the array exchange so a call with exchange[c] will cause a NullPointerException, because all array elements are initialized per default with null!

[Sierra]

In case you have such problem again you should also get the line in which the exception occurrs, right? If not you should determine that line - it helps you and us... ;)

[javano0b]

ok i changed it to

import java.util.Scanner;
import java.text.NumberFormat;

public class lab9

{
	public static void main( String [] args)
	{
		
		//foreign exchange;//
		final int Max = 20;
		foreign[] exchange = new foreign[Max];
		Scanner scan = new Scanner (System.in);
		String another = "Y";
		int c=0;
		
		
		do
		{
			foreign.titles();
			
			foreign.menu();
			//static methods called before the object is initiated

			exchange[c]= new foreign();
			
			//allows us to call the other methods
		
			exchange[c].getchoice();
			
			c = exchange[c].getchoice();
			
			if (c != 0)
			{	
			
				exchange[c].dollars();
				
				exchange[c].calculate();
		
				exchange[c].value();
			
				System.out.println(exchange);
			
				//above call methods from the other class
			}
			
		}
		while (c != 0);
		//tells the program to continue calculating as long as 0 is not selected

		System.out.println("display a summary report? Y/N");
		another = scan.nextLine();
		System.out.print("\nItemt\t\tConversion\t\t\tDollars\t\t\tAmount");
    	for (int i=0; i<c; i++)
			System.out.println(exchange[i]);
		foreign.displaycount();	
		//this static method is only called when the choice is 0 which is the end of the program 
			
	}

}

this allows me to run it and make a selection based on the menu but it wont run the if statement. (ie i select country 1 it should then ask for the dollar amount i want to convert them run the appropriate calculation.) How can i get the choice selected from the getchoice method to be the value for c so that the if statement will work.

[Sierra]

And you call exchange[c].getchoice(); twice, because... of what?

I find the whole structure disturbing... you have an array that uses c you get while using an object of that array. Is that really what you intend to do?