I'm trying to think of the best way to return an empty array, rather than null.
Is there any difference between foo() and bar()?
private static File[] foo() {
return Collections.emptyList().toArray(new File[0]);
}
private static File[] bar() {
return new File[0];
}
A different way to return an empty array is to use a constant as all empty arrays of a given type are the same.
private static final File[] NO_FILES = {};
private static File[] bar(){
return NO_FILES;
}
foo() worked disoriented me a bit. And I wasn't sure if referring to a constant would have any benefit. I don't know...just my inexperience, I suppose.
foo() be more preferable than bar(), where the solution you provided would be optimal?Both foo() and bar() may generate warnings in some IDEs. For example, IntelliJ IDEA will generate a Allocation of zero-length array warning.
An alternative approach is to use Apache Commons Lang 3 ArrayUtils.toArray() function with empty arguments:
public File[] bazz() {
return ArrayUtils.toArray();
}
This approach is both performance and IDE friendly, yet requires a 3rd party dependency. However, if you already have commons-lang3 in your classpath, you could even use statically-defined empty arrays for primitive types:
public String[] bazz() {
return ArrayUtils.EMPTY_STRING_ARRAY;
}
ArrayUtils.toArray() creates a new File[0] every time it is called, which can be easily checked with comparing hash codes.Definitely the second one. In the first one, you use a constant empty List<?> and then convert it to a File[], which requires to create an empty File[0] array. And that is what you do in the second one in one single step.
You can return empty array by following two ways:
If you want to return array of int then
Using {}:
int arr[] = {};
return arr;
Using new int[0]:
int arr[] = new int[0];
return arr;
Same way you can return array for other datatypes as well.
return new int[] {}return new File[0];
This is better and efficient approach.
There is no difference except the fact that foo performs 3 visible method calls to return empty array that is anyway created while bar() just creates this array and returns it.
I'm pretty sure you should go with bar();
because with foo(); it creates a List (for nothing) since you create a new File[0] in the end anyway, so why not go with directly returning it!
In a single line you could do:
private static File[] bar(){
return new File[]{};
}
new File[0] would to the same thing as new File[]{}, with less symbols, and I'd expect it to compile to the same bytecode.
foo()is advised only to hide what the code is doing.return 15 - 3*5 + 0;?foo()will return the array created as the parameter passed totoArray!