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I have an array with 8 elements, and I need to remove the first element from it and copy it to the same array. I tried it using System.arraycopy(...) but the size of the array did not change.

int[] array = {90,78,67,56,45,34,32,31};
System.arraycopy(array, 1, array, 0, array.length-1);

what I need is, the array should consist 78,67,56,45,34,32,31 elements with the array size of 7

there is a way to do this by copying this to another array and assigning it to the first array

int arrayB = new int[array.length-1];
System.arraycopy(array, 1, arrayB, 0, array.length-1);
array = arrayB;

but this is not the way I want. I need it to be done without the help of another array.

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  • 2
    arrays are fixed length in Java Commented Dec 5, 2015 at 4:22
  • Is there any reason why you are using arrays? I thing something like ArrayList could be a better choice? Commented Dec 5, 2015 at 4:39

3 Answers 3

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You cannot change the size of an array in Java. Therefore, what you are trying to do is impossible.

FWIW: the most concise way to copy to a >>new<< array reducing its size by one (as per your example) is:

int[] arrayB = Arrays.copyOfRange(arrayA, 1, arrayA.length);

And you can copy elements >>within<< an array using a loop, or using System.arrayCopy. The arraycopy javadoc says:

"If the src and dest arguments refer to the same array object, then the copying is performed as if the components at positions srcPos through srcPos + length - 1 were first copied to a temporary array with length components and then the contents of the temporary array were copied into positions destPos through destPos + length - 1 of the destination array."

In other words, you don't need to do an explicit double copy.

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2 Comments

So the method I mentioned is the only way to achieve this? (copying to another array and copy the second array to the first)
No it isn't. See my updated answer.
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Deleting an element from Java array and then shrinking array size is not a possibility in Java as arrays are of fixed length. Folks use different data structures like ArrayList etc whenever requirement is as such.

Lots of options have been put in here but none are one line answers that you are looking for.

delete-item-from-array-and-shrink-array
how-do-i-remove-objects-from-an-array-in-java

Of the options presented in above questions, I personally like the answer ,

Using ArrayUtils.removeElement(Object[],Object) from org.apache.commons.lang is by far the easiest way to do this.

Even in this case, the trick is to create a new array of new size and assign to same reference so original array is gone but yes, your application code is not required to create two arrays. Hope it helps !!

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0

I think you should try Arraylist<> in java

ArrayList arraylistobject = new ArrayList();

use for delete arraylistobject.remove(Object); it will automatic decrease size of arraylist.size(); try this one for your problem it is best.

why?

Array is static in size that is fixed length data structure, One can not change the length after creating the Array object. ArrayList is dynamic in size . Each ArrayList object has instance variable capacity which indicates the size of the ArrayList. As elements are added to an ArrayList its capacity grows automatically.

for more LINK

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