how to return an array from a method

[Manisekar Chinnasami]

class Test
{
public int methode()
{
int a = {1,2,3,4,5};
return a; // how to return it ??? return a[] or anyother way?
}
}

give me a solution ...

[Ernest Friedman-Hill]

Just like this:

public int[] methode() {
    int[] a = {1,2,3,4,5};
    return a; 
}

[vanlalhmangaiha khiangte]

Instead of returning a single integer in
public int methode()
Return an array of integers like
public int[] methode()

[Peter Chase]

Your problem isn't with the "return", it's with the earlier declaration of variable "a" and the declaration of the method. In both cases, you declared it as "int", but it is [a reference to] an array, so should have been declared "int[]".

Once your method and your variable "a" are declared as "int[]", you can just use "return a" to return [a reference to] the array.

[Manisekar Chinnasami]

when i tried to compile the following program, i got an incompatible type error ... (for returning an array) ....

import java.lang.reflect.Array;

class ResizeArray
{
static int z;
public int resizeArr(int [] b,int n)
{

z = n;
b = new int[10];
b = (int[])ArrayUtils.expand(b);
return b;

}

public static Object expand(Object a)
{
Class cl = a.getClass();
if (!cl.isArray()) return null;
int length = Array.getLength(a);
int newLength = z;
Class componentType = a.getClass().getComponentType();
Object newArray = Array.newInstance(componentType, newLength);
System.arraycopy(a, 0, newArray, 0, length);
return newArray;
}

public static void main(String args[])
{
ResizeArray ra = new ResizeArray();
int a[] = {1,2,3,4,5};
System.out.println("main length "+a.length);
int d=3;
ra.resizeArr(a,d);
}
}

watz the error in it ???

[Kelvin Chenhao Lim]

Hi Manisekar,

You forgot to change the return type of your resizeArr() method to declare an array return type:

public int[] resizeArr(int [] b,int n)
{
z = n;
b = new int[10];
b = (int[])ArrayUtils.expand(b);
return b;
}

[Manisekar Chinnasami]

yup ... you are correct, Kelvin. i didnt notice that ... thanks

[Bert Bates]

Hey Manisekar,

You've hit upon a very, very important idea in Java, and in OO languages in general. It's useful to think of the methods you create for your objects as message senders and receivers. As you get deeper and deeper into the language you'll see that a method's "signature" (in other words the messages it must receive and the message it returns) are always a crucial part of understanding the method itself - in many cases the ONLY thing you'll know about how a method works is what you must send to it, and what it will return to you. So, you're on the right track figuring out how to return an array!

Bert

[Mark Ii]

You can try the following code to do the same thing.

import java.util.Arrays;

public class ReturnArr {
	
	public static int[] retArr() {
		return new int[] {1,2,3,4,5};
	}
	
	public static void main(String[] args) {
		int[] anArray = retArr();
		
		System.out.println(Arrays.toString(anArray));
	}

}

[Mark Nathon]

Hi Manishekar, there is an easy way to return an array from a method in java. You can call a method by value or by reference.

one thing here to note that Java always passes arrays and vectors by reference. So, any modification to the array elements in another function would mean that the original array would also be modified similarly. However, returning arrays from a function is pretty simple. A method that returns an array needs to have the return type of the function set to the appropriate data type for the array.

Here is the code I got online from this article.

class Array
{
    public int[] returnArr()
    {
        int arr[] = { 1, 2, 3, 4, 5 };
        return arr;
    }

    public static void main(String args[])
    {
        Array obj = new Array();
        int a[] = obj.returnArr();
        for (int i = 0; i < a.length ; i++)
        {
            System.out.print(a[i]+" ");
        }
    }
}

I assume that you know how to pass the array. This code will help you learn how to return an array from a method.

[Stephan van Hulst]

Welcome to CodeRanch Mark!

Mark Nathon wrote:You can call a method by value or by reference.

No. In Java you can only call methods by value. When you pass an array to a method, you really pass a reference to the array, by value.

So, any modification to the array elements in another function would mean that the original array would also be modified similarly.

This is not what "pass by reference" means. Pass by reference means that the method parameter becomes an alias for a variable in the calling method. When you change the value of the parameter, you also change the value of the variable in the calling method directly. This is something completely different from passing array or object references by value.

The phrase "pass by reference" is meaningless for return values. A language that supports "pass by reference" only supports it for method parameters. However, Java doesn't support pass by reference at all.

[Campbell Ritchie]

Welcome to the Ranch (again)

Mark Nathon wrote:. . . You can call a method by value or by reference. . . . Java always passes arrays and vectors by reference. . . .

I see Stephan has already explained your mistake. Thank you for giving us that link It is unfortunate that people still write that sort of rubbish in tutorials.

Please don't call what you wrote a function; call it a method. It doesn't actually represent a function because it takes no input.

[Houssam El]

Hi,
I want to notice some hits, so when your write return a, you would know that you return an object reference, not the returned array, probably there were two possible to return the desired array, 1 - you tape new int[]{}{} or you use for loop and change the method to void type

[Campbell Ritchie]

Afraid your question isn't clear, HE.