Java, most efficient way to pass String array as Method Parameter

Question

I have the following code

String[] args = {"a", "b", "c"};
method(args);


private void method(String[] args){
    return args;
}

Why can I not do the following without errors?

method({"a", "b", "c"});

This code is example just to prove the point, not the actual methods I am using. I would like to do the second method instead to clean up my code, and avoid declaring a dozen different arrays when I only use them once to pass to my method.

The heart of the question is what is the most efficient way to pass an array of strings as a method paramter.

possible duplicate of [Why passing {a, b, c} to a method doesn't work?](http://stackoverflow.com/questions/1017486/why-passing-a-b-c-to-a-method-doesnt-work) see also [Java: array initialization syntax](http://stackoverflow.com/questions/5387643/java-array-initialization-syntax) and especially [Why array constants can only be used in initializers?](http://stackoverflow.com/q/10520617/139010) — Matt Ball, Jul 30 '13 at 07:31
Edited question, and redefined goal of answer to be more specifcly about most efficient way to pass array as parameters, provided links do not discuss varargs, therefor question should no longer be considered duplicate. — Dan Ciborowski - MSFT, Jul 30 '13 at 08:01
Incidentally, your edited question _still_ doesn't mention varargs. — Matt Ball, Jul 30 '13 at 14:40
I think you should ask a new question. You're asking *exactly* the same as the duplicate, and the added last sentence IMO doesn't change that at all. — Uli Köhler, Mar 02 '14 at 23:22

score 18 · Answer 1 · answered Jul 30 '13 at 07:30

18

try

method(new String[]{ "a", "b", "c"});

that way the system knows it is a new string-array.

java is not like php ;)

answered Jul 30 '13 at 07:30

bas

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Peter Lawrey · Accepted Answer · 2013-07-30T08:01:11.787

7

I suspect you want to use varargs. You don't even need to create an array to sent variable length arguments.

String[] strings = method("a", "b", "c");

private String[] method(String... args){
    return args;
}

or

String[] strings = array("a", "b", "c");

private <T> T[] array(T... args){
    return args;
}

or if you want to condense futher

String[] strings = array("a, b, c");

private String[] array(String args){
    return args.split(", ?");
}

edited Jul 30 '13 at 08:01

answered Jul 30 '13 at 07:34

Peter Lawrey

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Are there 3 "." after String because I had 3 Strings? – Dan Ciborowski - MSFT Jul 30 '13 at 07:36
1

And must a varargs parameter be the last parameter of a method? This is curiosity since not covered in original question. – Dan Ciborowski - MSFT Jul 30 '13 at 07:40
1

No, the number of periods has nothing to do with the number of Strings. It's the syntax for varargs. And yes, the varargs parameter needs to be last. – Kayaman Jul 30 '13 at 07:45
@djc391 No, there's not three dots because there are three strings. You can pass any number of strings. See [Varargs](http://docs.oracle.com/javase/1.5.0/docs/guide/language/varargs.html). – Jesper Jul 30 '13 at 07:45
What version of Java were Varargs added? – Dan Ciborowski - MSFT Jul 30 '13 at 07:47
1

@djc391 Java 5.0 in 2004. – Peter Lawrey Jul 30 '13 at 07:53
Taking this code as answer, over bas's answer because it saves having to write new String[] repeated times(in my case 22 instances) – Dan Ciborowski - MSFT Jul 30 '13 at 07:58
@djc391 If you want terse, you can use the third option. – Peter Lawrey Jul 30 '13 at 08:01

tbodt · Answer 3 · 2017-01-08T00:52:21.750

6

If you use:

method({ "a", "b", "c"});

then java has no idea whether you want an array of String or of Object. You can explicitly tell java what kind of array it is like this:

method(new String[] { "a", "b", "c"});

That way Java can tell that you mean an array of String.

edited Jan 08 '17 at 00:52

answered Jul 30 '13 at 07:37

tbodt

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score 2 · Answer 4 · answered Jul 30 '13 at 07:31

2

You do not need a named reference to the array. You can initialize and pass an anonymous array like this:

method (new String[]{"a", "b"});

answered Jul 30 '13 at 07:31

Philipp

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Java, most efficient way to pass String array as Method Parameter

4 Answers4