Why does Java allow arrays of size 0?

Question

Arrays in java are fixed in length. Why does Java allow arrays of size 0 then?

String[] strings = new String[0];

Answer 1

Why does Java allow arrays of size 1? Isn't it pretty useless to wrap a single value in an array? Wouldn't it be sufficient if Java only allowed arrays of size 2 or greater?

Yes, we can pass null instead of an empty array and a single object or primitive instead of a size-one-matrix.

But there are some good arguments against such an restriction. My personal top arguments:

Restriction is too complicated and not really necessary

To limit arrays to sizes [1..INTEGER.MAX_INT] we'd have to add a lot of additional boudary checks,(agree to Konrads comment) conversion logic and method overloads to our code. Excluding 0 (and maybe 1) from the allowed array sizes does not save costs, it requires additional effort and has an negative impact on performance.

Array models vector

An array is a good data model for a vector (mathematics, not the Vector class!). And of course, a vector in mathematics may be zero dimensional. Which is conceptually different from being non-existant.

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Sidenote - a prominent wrapper for an (char-)array is the String class. The immutable String materializes the concept of an empty array: it is the empty String ("").

Answer 2

Same as C++, it allows for cleaner handling when there is no data.

Answer 3

Another case when a zero length array is useful is when copying a two dimensional array. I can write:

public int[][] copyArray(int[][] array){
     int[][] newArray = new int[array.length][0];
     for(int i=0;i<array.length;i++){
         newArray[i] = array[i];
     }
     return newArray;

Being that every array reference in array is being overwritten, initializing them as refernces to zero length arrays is most efficient.