Accessing variable from different method

Question

Java Day 1 from c#. Just playing around with java (just for fun) and thought this example was interesting, the thing that gets me is how does bubblesort method access intArray? ok I know its being passed as a variable.. but its modifying the original array? I could understand of the bubblesort method printed the new array, but its the original method? Cool, but now sure how/why this is allowed? (hope I explained this properly)

public class HelloWorld {

public static void main(String[] args) {

    //create an int array we want to sort using bubble sort algorithm
    int intArray[] = new int[]{5,90,35,45,150,3};

    //print array before sorting using bubble sort algorithm
    System.out.println("Array Before Bubble Sort");
    for(int i=0; i < intArray.length; i++)
        System.out.print(intArray[i] + " ");

    //sort an array in descending order using bubble sort algorithm
    bubbleSort(intArray);

    System.out.println("");

    //print array after sorting using bubble sort algorithm
    System.out.println("Array After Bubble Sort");
    for(int i=0; i < intArray.length; i++)
        System.out.print(intArray[i] + " ");

    }

    private static void bubbleSort(int[] intArray){

    int n = intArray.length;
    int temp = 0;

    for(int i=0; i < n; i++){
        for(int j=1; j < (n-i); j++){

            if(intArray[j-1] < intArray[j]){
                //swap the elements!
                temp = intArray[j-1];
                intArray[j-1] = intArray[j];
                intArray[j] = temp;
            }
        }
    }        
    }
}

Oliver Charlesworth · Accepted Answer · 2011-09-19 23:59:44Z

4

Arrays are object types in Java, and so are accessed by reference. You pass a reference^* to the original array when you call the method, so the method accesses (and modifies) the original array.

_{* To all the sharp-eyed pedants, I'm being very careful to avoid the "you pass by reference in Java" fallacy.}

answered Sep 19, 2011 at 23:59

Oliver Charlesworth

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Comments

jpaoletti · Accepted Answer · 2011-09-20 01:55:47Z

0

Strictly talking, you are not modifying the array, you are moving its contents within positions

[1,3,2,4] => [1,2,3,4] is the same 4 lenght array but the content of the 2nd and 3rd position got they value changed.

answered Sep 20, 2011 at 1:55

jpaoletti

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