Passing arrays between methods

Question

I'm having difficulty passing arrays between methods, I've managed to set them all to false from boolean, and returned the array to the main. However from there I don't know how to pass it to another method, and then later display the boolean true array as "yes" or the boolean false array as "no". My code looks as follows:

import javax.swing.*;
class methodarrays
{
    public static void main (String[]param)
    {
        arrays();
        seen(); 
        display();
    }

    public static boolean[] arrays()
    {
        boolean [] birds = new boolean [5];
        for (int i=0;i<birds.length;i++)
        {
            birds[i]=false;
        }
        return birds;
    }
    public static boolean seen()
    {
        String quit = "100";
        String ans = "";
        while(!ans.eqauls(quit))
        {
            ans=JOptionPane.showInputDialog(null,"Which bird are you reporting? \n   1) Blue Tit   2) Blackbird   3)Robin   4)Wren   5)Greenfinch");
            if (ans.equals("1"))
            {
                birds[0] = true;
                return birds[0];
            }
            else if (ans.equals("2"))
            {   birds[1] = true;
                return birds[1];
            }
            else if (ans.equals("3"))
            {
                birds[2] = true;
                return birds[2];
            }
            else if (ans.equals("3"))
            {
                birds[2] = true;
                return birds[2];
            }
            else if (ans.equals("4"))
            {
                birds[3] = true;
                return birds[3];
            }
            else if (ans.equals("5"))
            {
                birds[4] = true;
                return birds[4];
            }
        }
    }

    public static void display()
    {
        JOptionPane.showMessageDialog(null,"Your Garden Watch results are:");
    }

}

You need to learn basic OO programming before asking such questions and read guides on "How to learn Java" — Adel Boutros, Nov 17 '15 at 15:27
Based on your implementation, whenever you call arrays() method you will automatically re-create birds array and re-set its content to False. I think at this stage it's difficult to understand what is your objective. — e.doroskevic, Nov 17 '15 at 15:28
@E.Doroskevic I'm attempting to change the boolean values, if a certain characters met. I want the boolean array to be one method and have it passed to the next methods — duldi, Nov 17 '15 at 15:30
@duldi I appreciate that, however your implementation does not reflect that. See, based on what you have coded-up, whenever you call method arrays() you will create an Array with 5 boolean values which by default are set to false. Given the array is in arrays() methods scope, you can pass it to another method only from arrays() method. — e.doroskevic, Nov 17 '15 at 15:33
As @AdelBoutros suggests, update an adjacent component in the listener to another component's model, as shown [here](http://stackoverflow.com/a/13919878/230513). — trashgod, Nov 17 '15 at 17:35

score 1 · Accepted Answer · answered Nov 17 '15 at 15:31

1

To give you are starting hand... you can set the result of your arrays method to a local variable in the main method and pass as a argument to the seen. Then you can do the same for the display method.

    public static void main (String[]param)
    {   
        boolean[] birds = arrays();
        seen(birds); 
        display(birds);
    }

    public static boolean[] arrays()
    {
    ...
    }
    public static boolean seen(boolean[] birds)
    {
    ...

There are plenty of tutorials around the web for this kind thing. Here being one example.

answered Nov 17 '15 at 15:31

George Lee

826
6
11

Thank you I will attempt this and let you know how i get on – duldi Nov 17 '15 at 15:31
Though I had to make a few changes, this did ultimately help me get closer to understanding the issue, thank you – duldi Nov 18 '15 at 16:56

score 1 · Answer 2 · answered Nov 17 '15 at 15:37

You need to pass it as a parameter or declare a global array.

Passing by parameter:

class methodarrays {

public static void main (String[]param)
{
    boolean [] myArray =arrays();
    seen(myArray); 
    display(myArray);
}

public static boolean seen(boolean [] myArrayParam)
{
   for (int i=0;i<myArrayParam.length;i++)
   {...}
}

public static boolean display(boolean [] myArrayParam)
{
   for (int i=0;i<myArrayParam.length;i++)
   {...}
}

}

As global array:

class methodarrays {

   boolean [] myArray

public static void main (String[]param)
{
    myArray = arrays();
    seen(); 
    display();
}

public static boolean seen()
{
   for (int i=0;i<myArray.length;i++)
   {...}
}

public static boolean display()
{
   for (int i=0;i<myArray.length;i++)
   {...}
}

}

score 1 · Answer 3 · answered Nov 17 '15 at 15:48

Declare

boolean [] birds = new boolean [5];

as accessible object for all methods within your class.

import javax.swing.*;

class methodarrays
{   

    private boolean [] birds = new boolean [5]

    ...

    public static boolean[] arrays()
    {
        for (int i=0;i<birds.length;i++)
        {birds[i]=false;
        }
        return birds;
    }

    ...
}

score 0 · Answer 4 · answered Nov 17 '15 at 15:42

Here is the implementation mimicing your own:

import javax.swing.JOptionPane;

public class Example { private static boolean [] birds = new boolean [5];

   public static void main (String[]param){ 
       arrays();
       seen(); 
       display();
   }

   public static boolean[] arrays()
   {   
       // Completely unnecessary since values are set to false by default;
       for (int i=0;i<birds.length;i++)
       {birds[i]=false;
       }
       return birds;
   }
   public static void seen(){   
       String quit = "100";
       String ans = "";
       while(!ans.equals(quit))
       {
           ans=JOptionPane.showInputDialog(null,"Which bird are you reporting? \n   1) Blue Tit   2) Blackbird   3)Robin   4)Wren   5)Greenfinch");
           if (ans.equals("1"))
           {   birds[0] = true;
           }
           else if (ans.equals("2"))
           {   birds[1] = true;
           }
           else if (ans.equals("3"))
           {   birds[2] = true;
           }
           else if (ans.equals("3"))
           {   birds[2] = true;
           }
           else if (ans.equals("4"))
           {   birds[3] = true;
           }
           else if (ans.equals("5"))
           {   birds[4] = true;
           }
       }
   }

   public static void display(){
       System.out.println("Your results are: ");
       System.out.println("Blue Tit: " + birds[0]);
       System.out.println("Blackbird: " + birds[1]);
       //and so on..
   }

}

It should be mentioned, the code above could be reduced substentially. However, the code has been kept to reflect the level of proficiency displayed in the OPs question. — e.doroskevic, Nov 17 '15 at 15:47

Passing arrays between methods

4 Answers4