How to add new element to Varargs?

Question

I have a method

public boolean findANDsetText  (String Description, String ... extra ) {

inside I want to call another method and pass it extras but I want to add new element (Description) to extras.

     object_for_text = getObject(find_arguments,extra);

How can I do that in java? What would the code look like?

I tired to accommodate code from this question but couldn't make it work.

Possible duplicate of [How to call a varargs method with an additional argument from a varargs method](http://stackoverflow.com/questions/27293989/how-to-call-a-varargs-method-with-an-additional-argument-from-a-varargs-method) — Raedwald, Dec 04 '15 at 13:06

score 13 · Answer 1 · answered Jul 04 '12 at 03:01

13

To expand on some of the other answers here, the array copy could be done a bit faster with

String[] newArr = new String[extra.length + 1];
System.arraycopy(extra, 0, newArr, 0, extra.length);
newArr[extra.length] = Description;

answered Jul 04 '12 at 03:01

Jonathan Callen

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score 5 · Answer 2 · answered Oct 04 '17 at 09:58

5

Use Arrays.copyOf(...) :

String[] extra2 = Arrays.copyOf(extra, extra.length+1);
extra2[extra.length] = description;

object_for_text = getObject(find_arguments,extra2);

answered Oct 04 '17 at 09:58

lenborje

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tsm · Accepted Answer · 2012-07-04T13:02:59.783

2

extra is just a String array. As such:

List<String> extrasList = Arrays.asList(extra);
extrasList.add(description);
getObject(find_arguments, extrasList.toArray());

You may need to mess with the generic type of extrasList.toArray().

You can be faster but more verbose:

String[] extraWithDescription = new String[extra.length + 1];
int i = 0;
for(; i < extra.length; ++i) {
  extraWithDescription[i] = extra[i];
}
extraWithDescription[i] = description;
getObject(find_arguments, extraWithDescription);

edited Jul 04 '12 at 13:02

answered Jul 04 '12 at 02:51

tsm

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1

I get `Cannot invoke asList() on the array type String[]` for the first option. – Radek Jul 04 '12 at 03:11
Did you mean to use `Arrays.asList(extra)`? (see Radek's comment). – Greg Kopff Jul 04 '12 at 03:14
Now I get `Cannot invoke toArray() on the primitive type boolean` for `Arrays.asList(extra).add(Description).toArray()` – Radek Jul 04 '12 at 03:30
Will given an `ArrayIndexOutOfBoundsException`. – Raedwald Dec 04 '15 at 13:05
4

This will no longer work (tested with Java 8u144) since Arrays.asList() returns an fixed-size List. Suggest to use Arrays.copyOf(...). – lenborje Oct 04 '17 at 09:54

score 1 · Answer 4 · edited Apr 08 '16 at 15:45

1

Do you mean something like this?

public boolean findANDsetText(String description, String ... extra)
{
    String[] newArr = new String[extra.length + 1];
    int counter = 0;
    for(String s : extra) newArr[counter++] = s;
    newArr[counter] = description;

    // ...

    Foo object_for_text = getObject(find_arguments, newArr);

    // ...
}

edited Apr 08 '16 at 15:45

Guido

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answered Jul 04 '12 at 02:52

Eng.Fouad

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score 0 · Answer 5 · answered Jul 04 '12 at 02:58

Its simply this way...

Treat the Var-args as below...

Example:

In your above example the 2nd parameter is "String... extra"

So you can use like this:

extra[0] = "Vivek";
extra[1] = "Hello";

Or

for (int i=0 ; i<extra.length ; i++)

  {

          extra[i] = value;

  }

score 0 · Answer 6 · answered Dec 03 '19 at 19:20

0

With Java 11 use as parameter for a new List:

List<String> templateArguments = new ArrayList<(Arrays.asList(args));
templateArguments.add(throwable.getMessage());
String.format(template, templateArguments.toArray());

answered Dec 03 '19 at 19:20

Leonardo Chassot

1

score 0 · Answer 7 · answered Feb 10 '20 at 15:04

0

Conversion to list and back to array, but shorter using utility functions:

// import com.google.common.collect.Lists;

var descriptionAndExtra
    = Lists.asList(description, extra).toArray(new String[extra.length + 1]));

answered Feb 10 '20 at 15:04

Raphael

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How to add new element to Varargs?

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