用{{}}进行数组实例化

Question

Looking for verification on the following:

Is there any difference between the following two

int [] arr = new int[]{1, 2, 3}; 

int [] arr2 = {1, 2, 3}; 

?

To me - none. in effect anyways. {1, 2, 3} instantiates as well initializing it. so-- no use at all invoking new ahead of it(?)

TIA.

Answer 1

No, there's no difference in the examples you gave. However, using new int[] allows you to separate the declaration and initialisation, as in:

int[] arr;
...
arr = new int[] { 1, 2, 3 };

whereas arr = {1, 2, 3}; would not be allowed.

Answer 2

There's no difference at all in the two examples shown, they're equivalent. But the first notation is needed, for instance if we have a method m() that receives as parameter, say, an int[] the only way to instantiate the array in-line would be:

m(new int[]{1, 2, 3});

Because this won't work:

m({1, 2, 3});

Why is this? it was defined to be like that by the language designers, probably to avoid ambiguities when parsing the code.

Answer 3

In the given example there is no differnce.

In general an array is either created by an array creation expression, eg using the new keyword ( §15.9 ) or an array initializer ( §10.6 ).

An array creation expression specifies the element type, the number of levels of nested arrays, and the length of the array for at least one of the levels of nesting. The array's length is available as a final instance variable length.

An array initializer creates an array and provides initial values for all its components.