If I create an array that can hold 10 objects, is it possible for that array to less then 10 objects?

I need to create an array that can hold 10 objects. If I make this array will it be able to hold less then the 10 object. An example would be the array has 7 objects and room for 3 more. Is this possible?

Yes. Assign null at some indices. Also, you can create the array without any objects stored in it, specifying the length.

Array is a data structure which stores a fixed-size sequential collection of elements of the same type. When you initialize an array, it can have at most the till the size of array, so for your answer it can have empty cells.

Yes. Arrays can hold any number of items up to, but not including the length you have allocated for it. In Java, arrays of primitive types (int, bool, double, char, etc.) will be filled with the default value of that type for any non-initalizer-list array, and null references for any arrays of Object types.

However, questions like yours are more suited for classroom discussion, as you may still be learning computer science material, it seems like.

It depends on what you mean.

All arrays have fixed length, and each always contains a number of elements exactly equal to its length. In that sense, no, arrays cannot have excess capacity; they are always completely filled. You can, however, keep track externally of which elements contain valid data, and ignore the others.

Technically, no array contains objects, but many contain references (of various types; as opposed to primitive values). It is conventional to be a bit sloppy with our language by calling those arrays of objects, and that's how I interpret the question. The distinction becomes important, however, when we recognize that any element of an array of references may contain the value null, which does not refer to an object. Thus, an array of references with some elements null refers to fewer actual objects than its length. You might characterize that as the array containing fewer objects than its length.

Note that null elements are not limited to the end of an array. They may appear at any index, interspersed with non-null elements.

With all that said, however, I suspect you're looking for Lists, and specifically java.util.ArrayList. Lists are more flexible than arrays in many ways, including that they have adjustable size. And ArrayList indeed does have a distinction between its current capacity and its current size, though the capacity is expanded as needed, not fixed like an array's length. The class name reflects that it is implemented with use of arrays, and its performance characteristics reflect that.

>I need to create an array that can hold 10 objects. If I make this array will it be able to hold less then the 10 object. An example would be the array has 7 objects and room for 3 more. Is this possible?

In short, yes. It will be able to hold 0 to 10 objects. However it doesn't mean your array can shrink and grow from 0 to 10. It will be a fixed size of 10 (be it you are using it or not).

The long answer is, there will always be 10 elements populated with some values (be it you are actively using all elements or not). Those elements which you think you are not using at the moment will still be populated with default value according to the data type of the array (i.e. null of object, 0 for integer, false for boolean).

For example, creating an int array of size 10:

int array[] = new int[10];

By default, you will already have 10 arrays (all populated with default 0).

Index:  0  1  2  3  4  5  6  7  8  9
Array: [0][0][0][0][0][0][0][0][0][0]

You will always have these 10 elements at your disposal. It is now up to you how you want use these 10 elements.

If you are looking for something that can shrink and grow. You can look into using java.util.ArrayList which can shrink/grow as you remove/add items into the list.