Array returning memory allocation instead of value in Java

Question

Consider a simple case like this one :

public static void array()
{
    String myString = "STACKOVERFLOW";
    int [] checkVal = new int[myString.length()];

    for(int i=0; i<myString.length();i++){
        checkVal[i] = (int)myString.charAt(i);
    }

    System.out.println(checkVal[0]);
    System.out.println(checkVal[1]);
    System.out.println(checkVal[2]);
    System.out.println(checkVal[3]);
    System.out.println(checkVal[4]);
    System.out.println(checkVal);
}

This will output the following :

83
84
65
67
75
[I@fc9944

Can some one please explain this to me ? How can I retrieve the proper information from the Array instead of it's memory allocation ?

score 8 · Accepted Answer · edited Jun 20 '20 at 09:12

If you want it pretty printed, use Arrays.toString to do it:

System.out.println(Arrays.toString(checkVal);

If not, it will just print out the toString of the array, which is inherited from Object, and generated a String contains its type and the hash code:

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. In other words, this method returns a string equal to the value of:

getClass().getName() + '@' + Integer.toHexString(hashCode())

This answer also has relevant info.

Now I understand what is going on ... Thanks ! – hayonj May 19 '13 at 17:16 — hayonj, May 19 '13 at 17:16

LanternMike · Answer 2 · 2013-05-19T17:10:29.300

0

after checkVal[4] you reference checkVal without an index []. this seems to correspond to your garbage line. if you are trying to get all values to print in the final System.out, seems you could do a loop through the array and keep apending the values to a string with a space in between numbers, and then print that string.

edited May 19 '13 at 17:10

answered May 19 '13 at 17:02

LanternMike

664
1
5
16

garbage line ? i hear about garbage collector but still have no idea what it represent ... i didn't get that far – hayonj May 19 '13 at 17:04
i mean what you see for the 6th line printing, [I@fc9944 is the 6th systemOut line where you systemOut checkVal not checkVal[5] – LanternMike May 19 '13 at 17:05

score 0 · Answer 3 · answered May 19 '13 at 17:20

When you try to print any object's value, its toString() method is called(inherited from Object class). If the class does not override this method then super class implementation of this method is invoked. Object class toString method returns the hashcode of the object.

The output that you saw was the hashcode of the array object. So to print the values of the array object you need to iterate through it and print all the values. Or else other solution could be to use Collections like List or Set(i.e. dynamic array) which will print the values all the values within it when its toString() method is called.

Difference between collections like ArrayList and simple Array is that, List's can grow or shrink dynamically as needed(i.e. its size is variable). It also provides many in-build API methods to perform various operations on the List.

Array returning memory allocation instead of value in Java

3 Answers3

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