Thread: Need help with creating method for Array.

A quickly brief history of my Homework assignment.

Using the code examples that you created, sort the following items: Rocket J. Squirrel, Bullwinkle J. Moose, Boris Badenov, Natasha Fatale, Fearless Leader, Mr. Big, Cloyd, Gidney, Metal-Munching Moon Mice, Capt. Peter "Wrongway" Peachfuzz, Edgar, and Chauncy
Your program should perform the following tasks.
1. Read the data in from the keyboard into the array interactively.
2. Print the array.
3. Sort the array in ascending order using the bubble sort;
4. Print the array;
5. Sort the array in descending order using the bubble sort;
6. Print the array.
Further specification:
You must use a separate method for each task.
There must be a method for loading the data into the array.
There must be one and ONLY one method for printing the contents of the array.
There must be a method for sorting the array in ascending order.
There must be a method for sorting the array in descending order.
If you do not use the bubble sort in the methods which sort the data, do not bother handing your code in to me.

The list of names is long. Save yourself some aggravation with these two suggestions:
1. Use the nextLine() method to read the String data from the keyboard into the array.
2. Do NOT enter all the data each time you test. Start by entering only one character instead of
each full name. Enter all of the entire names when you are sure all of your sorting and printing
algorithms are running correctly.

 
import java.util.*;
 
public class lab7
{
    public static void main (String[] args)
    {
 
 
 
    String x = " ";
    String x1 = "";
    x1 = storedList(x);     
    printArray(x1);
 
 
 
    }
 
 
    public static String storedList( String stored)
    {
        Scanner scan = new Scanner(System.in);
 
        String[] list = new String[12];
 
        System.out.println( "Hello user, I will sort your list in asscending and descending order?  ");
        System.out.println( "Please enter your string." );
        for( int i = 0; i <=11; i++)
        {
            list[i] = scan.nextLine();
        }
 
        return stored;
    }
 
    public static void printArray(String[] displayed)
    {
 
     String[] list = new String[12]; 
 
     for (int i = 0; i <= 11; i++)
         {
         System.out.print( list[i] + " " );
         }
 
    }  
 
}

What I'm having issues is passing arguments into each method. I was able to figure out how to make one method to accept my array. But I'm having trouble creating a method to print the array. I keep receiving this compiler error. Please refer to screen shot. PLEASE help!

complier_errro.jpg

Thanks Again!

method printArray in class lab7 cannot be applied to given types;
requried:java.lang.String[]; found java.lang.String; reason: actual argument java.lang.String cannot converted to java.lang.String by method invocation conversion

The operator that you use here cannot be used for the
typed of value that you are using it for. You are either
using the wrong type here, or the wrong operator.

I'm using blueJ so I'm sorry it doesn't refer to line. It just flash to the problem code which is this.

printArray(x1);

The error message tells you what the problem is. Look at how the printArray method is defined ---

    public static void printArray(String[] displayed)
    {
 
     String[] list = new String[12]; 
 
     for (int i = 0; i <= 11; i++)
         {
         System.out.print( list[i] + " " );
         }
 
    }

What is the type of parameter that it's supposed to accept?
What type is actually passed in by you when you call the method?

And actually, the error message answers my questions nicely:
requried:java.lang.String[];
found java.lang.String;

Also: What is the purpose of the method storedList()? What is it supposed to get from the user?

Well I know where my issue is. For some apparent reason after calling my storedList I want to send this array to the print method to print the array. The method should be reusable. But I'm having trouble inputting this array in this method. I keep receiving this compiler I don't see any issues in my code. Does that help?

So you understand that the method requires that an array be passed into it, and you're not passing in an array, right? You're passing in a single String. So look to see where you get that single String in the first place. It is here that you should be receiving an array of String. Keep tracing back into your code to see why this error is occurring. If you look carefully, you'll see the error.

Sure thing,

There should be a method named storedList

storedList should ask the user for Strings value(12 to be precise). Each string value should be stored in the array in the storedList method. Once the strings values are stored I want to return the array. And then print the array in the printArray method.

I think that's where I'm having allot of issue at. For some reason I don't think I'm returning an array after running the method. Below is the method that is suppose to ask for the String.

 
    public static String storedList(String[] stored)
    {
        Scanner scan = new Scanner(System.in);
 
        String[] list = new String[12];
 
        System.out.println( "Hello user, I will sort your list in asscending and descending order?  ");
        System.out.println( "Please enter your string." );
        for( int i = 0; i <=11; i++)
        {
            list[i] = scan.nextLine();
        }
 
        return stored;
    }

I have looked in my book on how store arrays. But it said nothing about storing String or char values into methods. I know how to do with numbers but not Strings. Do you have any suggestions?

Originally Posted by Rain_Maker

I think that's where I'm having allot of issue at. For some reason I don't think I'm returning an array after running the method.

Your code will tell you what you're returning. What variable are you returning? What type is it? I've been trying to get you to look critically at this method. Please do so. Why are you creating an array, list, and completely ignoring it when the method returns? Why have you changed the parameter to an array, as that makes no sense?

edit: sorry, the above was posted in frustration. The key is to think through what you're doing before you type in code. Usually in a method like this, you'll create something of interest, here the list, and then *return* that item of interest, again the list. Else you're creating the object for no purpose whatsoever. And you don't want to make random senseless changes to your code like making the parameter an array when it is not supposed to be one.

Okay I see I have corrected my method.

 
import java.util.*;
 
public class lab7
{
    public static void main (String[] args)
    {
 
    String test, test1;
    test = " ";
    test = storedList(test);
 
    printArray(test);
 
 
 
    }
 
 
    public static String storedList(String stored)
    {
        Scanner scan = new Scanner(System.in);
 
        String[] list = new String[12];
 
        System.out.println( "Hello user, I will sort your list in asscending and descending order?  ");
        System.out.println( "Please enter your string. Press enter for each string value." );
 
        int i; 
        for ( i = 0; i <=12; i++)
        list[i] = scan.nextLine();
 
        return list[i];
    }
 
    public static void printArray(String displayed)
    {
       String list[] = new String[12];
 
       for (int i = 0; i <= 11; i++)
       System.out.print( list[i] + " " );      
    }  
 
}

It took me long time to understand what was really the problem. But it seems like after I fix one thing its another problem. When running my code I have another issue. I don't receiving an compiler error but another area when running my terminal.

Hello user, I will sort your list in asscending and descending order?
Please enter your string. Press enter for each string value.
a
b
c
d
e
d
f
g
h
j
y
t
h
java.lang.ArrayIndexOutOfBoundsException: 12
at lab7.storedList(lab7.java:38)
at lab7.main(lab7.java:17)

I know that for some reason instead of the method ending after storing the array. Its continuing after 12th memory block has been inserted in the array. smh ***sigh***

When you say they should use the length field, what are you referring to? I'm a little confuse from what I seen in my text book it uses example which hard coded values are in place to run through the for loop.

--- Update ---

Thank you all for being patient with me by the way.

Arrays have a length field that should be used:

// for array myArray...
for (int i = 0; i < myArray.length; i++) {
 
}

I still receive the same error message. I been playing around with it but I receive the same results.

public class lab7
{
    public static void main (String[] args)
    {
 
    String test, test1;
    test = " ";
    storedList(test);
 
  //  printArray(test);
 
 
 
    }
 
 
    public static String storedList(String stored)
    {
        Scanner scan = new Scanner(System.in);
 
        String[] list = new String[12];
 
        System.out.println( "Hello user, I will sort your list in asscending and descending order?  ");
        System.out.println( "Please enter your string. Press enter for each string value." );
 
        int i = 0; 
 
            for ( i = 0 ; i <= list.length; i++)
            {
                list[i] = scan.nextLine();
            }
 
            return list[i];
 
 
    }
 
      // public static void printArray(String displayed)
       // {
       //String list[] = new String[12];
 
       //for (int i = 0; i <= list.length; i++)
      // System.out.println( list[i] + " " );      
      //  }  
 
}

Ouput below
Hello user, I will sort your list in asscending and descending order?
Please enter your string. Press enter for each string value.
a
b
c
d
e
f
g
h
i
j
k
f
e

java.lang.ArrayIndexOutOfBoundsException: 12
at lab7.storedList(lab7.java:39)
at lab7.main(lab7.java:17)
****sigh****

Please look carefully at your for loop vs. mine. There is a critical difference.

You put less than instead of less than or equal too.

Originally Posted by Rain_Maker

You put less than instead of less than or equal too.

Exactly. Remember that arrays are 0 based, and so if an array has length of 8, it will hold items in spots using indices 0 to 7. When you loop until i < myArray.length your for loop stops before the index reaches the length of the array, which is what you want. Again if myArray has a length of 8, it will have 8 items going from myArray[0] to myArray[7]. If I used <=, I would be trying to obtain item myArray[8] which doesn't exist and which throws the exception that you are seeing.

I understand but for some reason when I run the program again I receive the same error.

 
    public static String storedList(String stored)
    {
        Scanner scan = new Scanner(System.in);
 
        String[] list = new String[12];
 
        System.out.println( "Hello user, I will sort your list in asscending and descending order?  ");
        System.out.println( "Please enter your string. Press enter for each string value." );
 
        int i; 
 
        for ( i = 0 ; i < list.length; i++)
        {
        list[i] = scan.nextLine();
        }
 
        return list[i];
 
    }

(On this line)return list[i];

java.lang.ArrayIndexOutofBoundsExcepetion

which mean my return value is returning a value of bounds. But I don't know why its returning out bound when its clearly not out of bounds. The list array has 12 place orders for each string value. So why is it still giving me this error message? I'm doing something but I don't know what.

When you use the [ ]operators you are asking for one element of the whole array, in your method at the end of the for loop i is equal to list.length (12) which terminates the for loop but then are attempting to reference the 12th element of your String array ie. A single String (not an entire array of them) which is causing OutOfBoundsException... Compare your for loop to curmudgeon's, you'll notice that after his has terminated calling store[i] would not be possible...
Regardless of all this you're returning the wrong data type still...

Norm I want to return the whole array. I want the array to have all my string data.