How to add new element to Varargs?

问题

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.

回答1:

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);

回答2:

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;

回答3:

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);

    // ...
}

回答4:

Use Arrays.copyOf(...) :

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

object_for_text = getObject(find_arguments,extra2);

回答5:

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";

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

  {

          extra[i] = value;

  }

回答6:

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());

来源：https://stackoverflow.com/questions/11321784/how-to-add-new-element-to-varargs

标签

java

variadic-functions