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Thread: Learning Java

  1. #1
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    Default Learning Java

    I am trying to use two methods in one program class. The first one works to give a simple list of numbers from a "for loop." I want to have the second method take those list of numbers and convert them (as a string) into an array. One problem is how to give them proper names.

    Here is the code:
    public class Example2 {
     
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
     
    		//call method
    		//this works to call the method of numbers below
    		Numbers();
     
    		//call method to convert string of numbers to character Array
    		Convert();
    	}
     
    	public static int Numbers()
    	{		
    		for (int i = 0;i < 10; i++)
    		{
    		System.out.println (i);
    		}	
    	return 0;
    		//why use return 0?
    	}
     
    	public static int Convert()
    	{
    		//error is with labeling it with Numbers as I try... 
    		//...to pass the list of numbers to this method
    		String Numbers = null;
    		char[] CharArray = Numbers.toCharArray();
    		System.out.println(CharArray);
     
    		return 0;
    	}
    }


  2. #2
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    Default Re: Learning Java

    In order to make the code easier to read, place it inside code tags (the # sign wraps the selected text in code tags).

    Can you give an example of what the expected results should be?

  3. #3
    mmm.. coffee JavaPF's Avatar
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    Default Re: Learning Java

    Quote Originally Posted by Zymus View Post
    In order to make the code easier to read, place it inside code tags (the # sign wraps the selected text in code tags).
    We are trying to replace the code tags with the highlight tag (please see my signature)
    I have edited the post and added them for you this time.
    Please use [highlight=Java] code [/highlight] tags when posting your code.
    Forum Tip: Add to peoples reputation by clicking the button on their useful posts.

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    mmm.. coffee JavaPF's Avatar
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    Default Re: Learning Java

    I've looked over your code.

    	public static int Numbers()
    	{		
    		for (int i = 0;i < 10; i++)
    		{
    		System.out.println (i);
    		}	
    	return 0;
    		//why use return 0?
    	}

    You say why return 0? Well with a method like this you have to return the variable type. So in this case it needs to return an integer value. So you could return 0, 100, 420 or any integer value.

    You could change int to void in which case you wouldn't need to return anything.

    	public static void Numbers()
    	{		
    		for (int i = 0;i < 10; i++)
    		{
    		System.out.println (i);
    		}	
    	}

    To pass the value of i to the next method I would call Convert() within your for loop and update the Convert method like so:

    	public static void Numbers()
    	{		
    		for (int i = 0;i < 10; i++)
    		{
    		//System.out.println (i);
    		Convert(i);
    		}	
     
    	}
     
    	public static void Convert(int i)
    	{
    		System.out.println(i);
    	}

    Try it for yourself..
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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    Default Re: Learning Java

    Thanks. JavaPF's code example worked. My goal of the program is the take the list of numbers (zero to 9) and put them into an array of numbers.

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    Default Re: Learning Java

    The first method just gives a list of numbers (0 to 9). I am trying to take that list output and use the second method to convert the list to an array. Then I can work with each element of the array. But how do I label the string to array conversion?
    Will it be convert.toCharArray or numbers.toCharArray? Or is there a better way to convert to an array?

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    Default Re: Learning Java

    Quote Originally Posted by jgc1 View Post
    The first method just gives a list of numbers (0 to 9). I am trying to take that list output and use the second method to convert the list to an array. Then I can work with each element of the array. But how do I label the string to array conversion?
    Where is the array that you want to manipulate in your code?

    For loops are good for populating arrays but first you must have an array to populate. In the code that you have posted in the OP, your method Numbers() only returns one value and only does so once, because it is only called once.

    What is happening in your first method is that the output is being printed to the console, but it is not being stored anywhere for further manipulation. There might be a way to recapture the output printed to the console, but it is arguably more straightforward to place the values into an array and then print the array to the console.

    Quote Originally Posted by jgc1 View Post
    Will it be convert.toCharArray or numbers.toCharArray? Or is there a better way to convert to an array?
    A brief notational comment:

    If you are referring to the methods that you have written, it is clearer to refer to them as convert(), numbers(), and toCharArray().

  8. #8
    Junior Member TopdeK's Avatar
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    Lightbulb Re: Learning Java

    Is this useful to you at all?

    - Main now has 2 arrays declared in it called intArray and charArray. intArray is for the storage of the values created in numbers.

    - Numbers() method takes the intArray, stores the values for later use but also prints out each value to the screen...as you wanted.

    - Convert() method takes the filled intArray and the empty charArray and converts each of the numbers (0 - 9) to their respective char version using the Character method, forDigit(). Then they are stored in charArray.

    - charArray is printed to the screen.

    *NOTE* Character.forDigit(numbers[x], 10) is there because I know the values wont exceed past the value 9. This won't work if your values exceed the value 9.

    public class Example2 {
     
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
     
    		//DECLARE ARRAYS
    		int[] intArray = new int[10];
    		char[] charArray = new char[10];
     
    		//call method
    		//this works to call the method of numbers below
    		intArray = Numbers(intArray);
     
    		//call method to convert string of numbers to character Array
    		charArray = Convert(intArray, charArray);
     
                    //print charArray to screen
    		for(int i = 0; i < 10; i++)
    		{
    			System.out.print(charArray[i] + " ");
    		}
    	}
     
    	public static int[] Numbers(int[] numbers)
    	{
    		System.out.print("These are the ints: ");
    		for (int i = 0; i < 10; i++)
    		{
    			numbers[i] = i;	//Store number in an integer array
    			System.out.print(numbers[i] + " "); //Print each number to screen
    		}
    		System.out.println("");
     
    		return numbers;
    	}
     
    	//Returns an array of numbers as characters
    	//@PARAM The array to be converted
    	//and The array to store the conversions
    	public static char[] Convert(int[] numbers, char[] converted)
    	{
    		System.out.print("These are the chars: ");
    		for(int i = 0; i < converted.length; i++)
    		{
    			converted[i] = Character.forDigit(numbers[i], 10);
    		}
     
    		return converted;
    	}
    }

    Output:
    L:\Code\Java\java Exercise2
    These are the ints: 0 1 2 3 4 5 6 7 8 9
    Theses are the chars: 0 1 2 3 4 5 6 7 8 9
    Last edited by TopdeK; May 6th, 2011 at 07:58 PM.

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