Variable parameter class?

Question

The following code

    public static void main(String[] args) {
        fun(new Integer(1));
    }
    static void fun(Object ... a) {
        System.out.println(a.getClass());
    }

gives the output :-

class [Ljava.lang.Object;

What class is this?

Thomas Jung · Accepted Answer · 2009-09-29 08:55:49Z

7

An Object[] array.

To get the runtime type information:

a.getClass().isArray() -> true
a.getClass().getComponentType().getName() -> java.lang.Object

edited Sep 29, 2009 at 8:55

answered Sep 29, 2009 at 8:50

Thomas Jung

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Comments

dfa · Accepted Answer · 2009-09-29 09:50:48Z

6

according to the JVM specifications it is simply an array of java.lang.Object:

[ means a monodimensional array
LfullyQualifiedName; means a class, L; is just syntax

edited Sep 29, 2009 at 9:50

answered Sep 29, 2009 at 8:54

dfa

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1 Comment

dfa Over a year ago

it is used only as delimiter, no special meaning; did you read the specifications?

Jesper · Accepted Answer · 2009-09-29 09:11:26Z

1

This is how varargs (methods with a variable number of arguments) work in Java - the varargs argument will look like an array inside the method.

answered Sep 29, 2009 at 9:11

Jesper

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