Array reference explanation

Question

For the code

int []arr = new int[4];
System.out.println(arr);

The output looks something like

[I@54640b25

What exactly is the compiler printing out? The memory address of arr? Unlike C, Java does not seem to equate the array name (in isolation) with the first position of the array.

A good question, but I believe it has already been addressed here. Possible duplicate of [How to use the toString method in Java?](http://stackoverflow.com/questions/3615721/how-to-use-the-tostring-method-in-java) — Paul Richter, Mar 19 '14 at 13:58

Maroun · Accepted Answer · 2014-03-19T14:00:46.407

6

In Java, each object has toString() method, and arrays are objects. The default is displaying the class name representation, then adding "@" and then the hashcode:

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object

Try to print the following line and you should get the same output:

int[] arr = new int[5]; 
System.out.println(arr.getClass().getName() + "@" + Integer.toHexString(arr.hashCode()));

edited Mar 19 '14 at 14:00

answered Mar 19 '14 at 13:53

Maroun

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and to add, arrays are objects in java unlike C. – codingenious Mar 19 '14 at 13:54
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Passing in arr as an argument to println() automatically calls arr's toString() method? – Stumbler Mar 19 '14 at 13:58
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@Duncan, just to clarify passing any object in println() automatically calls that object's toString. – codingenious Mar 19 '14 at 14:02

Salah · Answer 2 · 2014-03-19T14:04:19.480

3

Use the following in order to print the value of array:

Arrays.toString(arr);

Using System.out.println(arr) directory will print use the default toString method which returns:

object.getClass().getName() + "@" + Integer.toHexString(object.hashCode())

edited Mar 19 '14 at 14:04

answered Mar 19 '14 at 13:55

Salah

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Array reference explanation

2 Answers2