array output not correct

Question

I am using 2 classes and a bunch of methods to store something in an array then writing it to a file. After I write something to a file, instead of being of the var double, this is my code:

public void storeArray(Quest1 a, Quest2 b, String filename) throws   FileNotFoundException{

PrintWriter k = new PrintWriter(filename);
for(int i = 0; i < a.getDays(); i++)
{
    k.println(b.storeArr(a));
}

k.close();
System.out.println("Written.");
}

Quest 1 is a class, Quest 2 is a class and String filename is just getting passed through. After doing all that and putting the Quest3 object in my main menu. I run the program, input all my values etc which get put into an array in the class Quest 2 and then I write them to a file.

I open that file to check if it has worked and i get this:

     [D@264532ba

How do I fix that to get my double variables in the file?

zw324 · Accepted Answer · 2013-05-21 19:19:28Z

3

Print out Arrays.toString instead of just print out the array (which invokes its toString inherited from Object):

k.println(Arrays.toString(b.storeArr(a)));

Or if you want some custom format, you can use StringUtils.join from Apache Commons. Or, perhaps just write a loop if you cannot use any dependencies.

The thing you output is the toString of the array, which is its type ([D) + @ + its hash code (264532ba).

answered May 21, 2013 at 19:19

zw324

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4 Comments

roro Over a year ago

i did that, not its printing in 2 dimensions, i dont have 2 dimensions

zw324 Over a year ago

It returns the value of the array joined with , and enclosed in [], but what do you mean by "2 dimensions"?

roro Over a year ago

i thought that was 2 dimensions, sorry. but i understand now. why exactly does it print it enclosed [] with that?

zw324 Over a year ago

That's how it works, I can't say why: docs.oracle.com/javase/6/docs/api/java/util/… All the others are working in the same way.

Community · Accepted Answer · 2020-06-20 09:12:55Z

Arrays use the default implementation of toString() and that's why the output of the array is:

[D@264532ba

You have two options to print an array's content:

Iterate over each element.
Use Arrays.toString(array).

Explanation of the weird output

Let me explain the following code:

double[] array = new double[10];
System.out.println(array);

array is an object, hence you are calling println(Object) of PrintStream (System.out), which calls toString() on the passed object internally. The array's toString() is similar to Object's toString():

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

So the output would be something like:

[D@756a7c99

where [ represnts the depth of the array, and D refers to double. 756a7c99 is the value returned from hashCode() as a hex number.

Comments

Jason Bristol · Accepted Answer · 2013-05-21 19:31:43Z

0

This here:

k.println(b.storeArr(a));

You are printing b.storeArr(a) which is an array object.

Just do this:

PrintWriter k = new PrintWriter(filename);
for(int i = 0; i < a.getDays(); i++)
{
    b.storeArr(a);
    k.println(Arrays.toString(b));
}

edited May 21, 2013 at 19:31

answered May 21, 2013 at 19:25

Jason Bristol

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