Significance of "Object..."

Question

While going through various programs recently, I saw following code:

protected Object doInBackground(Object... arg0)
{
    ....
    ....
    ....
}

I dont understand the significance of Object...

I have never seen ... after any data type.

This is for Variable length argument. you can pass one argument ,two argument or as much you like. and in the method these can be get as array Of objects. http://docs.oracle.com/javase/1.5.0/docs/guide/language/varargs.html — Nirbhay Mishra, Apr 03 '13 at 10:56

score 6 · Accepted Answer · edited May 23 '17 at 11:55

6

It is called as variable arguments or simply var-args, Introduced in java 5. If you method accepts an var-args as a parameter, you can pass any number of parameters to that method. for instance below method calls would all succeed for your method declaration:

 doInBackground(new Object());
 doInBackground(new Object(), new Object());
 doInBackground(new Object(), new Object(), new Object());
 doInBackground(new Object(), new Object(), new Object(), new Object());

A previous post should give you more information Can I pass an array as arguments to a method with variable arguments in Java?

edited May 23 '17 at 11:55

Community

1
1

answered Apr 03 '13 at 10:35

PermGenError

45,977
8
87
106

1

correction : varargs was Introduced in java 5. – codeMan Apr 03 '13 at 10:42
@codeMan oops, true.. :) – PermGenError Apr 03 '13 at 10:43

Sami N · Answer 2 · 2013-04-03T10:43:14.897

3

See "Arbitrary Number of Arguments" from http://docs.oracle.com/javase/tutorial/java/javaOO/arguments.html

It's a shortcut to creating an array manually (the previous method could have used varargs rather than an array).

You can input an arbitrary number of Object-parameters to doInBackground. They are then accessible through the arg0 array in your method. arg0[0], arg0[1], and so on.

edited Apr 03 '13 at 10:43

answered Apr 03 '13 at 10:35

Sami N

1,170
2
9
21

score 0 · Answer 3 · answered Apr 03 '13 at 10:35

0

You can think of Object as a parent of all the runtime Instances of userdefined classes in java. The "..." refers to Varargs in java. Here is an example of varargs. It will be essentially interpreted as Arrays.

answered Apr 03 '13 at 10:35

codeMan

5,730
3
27
51

score 0 · Answer 4 · answered Apr 03 '13 at 10:36

0

Object is the base type for all classes in Java, except the primitives.

The three dots signify any number of arguments can be passed, aka varargs.

answered Apr 03 '13 at 10:36

NimChimpsky

46,453
60
198
311

score 0 · Answer 5 · answered Apr 03 '13 at 10:36

... allows you to provide multiple arguments called varargs.

doInBackground(1, "hello", "world");

This is how the MessageFormat.format method works which allows you to specify a format and then objects to fill that format.

public static String format(String pattern,
                            Object... arguments);

//Usage
MessageFormat.format("hello {0}, I'm from {1}", "John", "Earth");

score 0 · Answer 6 · answered Apr 03 '13 at 10:38

0

Its the way we tell that any number of arguments of a specific data type can be sent, rather than writing in 'n' number of times in function def. Check this.

answered Apr 03 '13 at 10:38

Anuj Balan

7,629
23
58
92

score 0 · Answer 7 · answered Apr 03 '13 at 10:39

0

This is actually a variable length or arguments in a method. When you will call this method you may pass n number of objects of Object class to this method and arg0 will be you array ob Objects. It's very old and very simple. Nothing else..

answered Apr 03 '13 at 10:39

Saurabh Agarwal

323
2
6
16

score 0 · Answer 8 · answered Apr 03 '13 at 10:39

0

Ellipsis or (...) is known as var-args. In this case, it made the method very generalized method. it can take any number and any type of argument.

answered Apr 03 '13 at 10:39

Ankit

6,554
6
49
71

Significance of "Object..."

8 Answers8