Java method with array argument

pass array to method Java

Just pass it as any other variable.
In Java, arrays are passed by reference.

so. If I change the array (passed in as parameter) in a method, do I change the values in the original array in caller?

@Remian8985 If the array is declared globally or if you’re accessing it through its class (e.g, someClass.array), then yes.

yeah arrays are implemented as objects in Java and hence its only just necessary to pass a reference of the array to the method you want to invoke.

Simply remove the brackets from your original code.

PrintA(arryw); private void PassArray() < String[] arrayw = new String[4]; //populate array PrintA(arrayw); >private void PrintA(String[] a) < //do whatever with array here >

Heh, I think we’ve all done that before. What I’d like to know is why we still have to initialize our objects explicitly. Is there any situation where we WANT a typed null pointer? Even if so, it’s definitely an exception rather than the norm.

An array variable is simply a pointer, so you just pass it like so:

A little more elaboration. If what you want to do is create a COPY of an array, you’ll have to pass the array into the method and then manually create a copy there (not sure if Java has something like Array.CopyOf() ). Otherwise, you’ll be passing around a REFERENCE of the array, so if you change any values of the elements in it, it will be changed for other methods as well.

There is an important point of arrays that is often not taught or missed in java classes. When arrays are passed to a function, then another pointer is created to the same array ( the same pointer is never passed ). You can manipulate the array using both the pointers, but once you assign the second pointer to a new array in the called method and return back by void to calling function, then the original pointer still remains unchanged.

You can directly run the code here : https://www.compilejava.net/

import java.util.Arrays; public class HelloWorld < public static void main(String[] args) < int Main_Array[] = ; Demo1.Demo1(Main_Array); // THE POINTER Main_Array IS NOT PASSED TO Demo1 // A DIFFERENT POINTER TO THE SAME LOCATION OF Main_Array IS PASSED TO Demo1 System.out.println("Main_Array = "+Arrays.toString(Main_Array)); // outputs : Main_Array = [20, 19, 18, 4, 16, 15, 14, 4, 12, 11, 9] // Since Main_Array points to the original location, // I cannot access the results of Demo1 , Demo2 when they are void. // I can use array clone method in Demo1 to get the required result, // but it would be faster if Demo1 returned the result to main > > public class Demo1 < public static void Demo1(int A[]) < int B[] = new int[A.length]; System.out.println("B = "+Arrays.toString(B)); // output : B = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] Demo2.Demo2(A,B); System.out.println("B = "+Arrays.toString(B)); // output : B = [9999, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] System.out.println("A = "+Arrays.toString(A)); // output : A = [20, 19, 18, 4, 16, 15, 14, 4, 12, 11, 9] A = B; // A was pointing to location of Main_Array, now it points to location of B // Main_Array pointer still keeps pointing to the original location in void main System.out.println("A mt24">
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)">edited Feb 16, 2017 at 8:04
answered Feb 16, 2017 at 7:57
 
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