3 dot in parameter in Java

Question

Can someone explain the meaning of the 3 dots, that we always use in our main method in Java?

public static void main(String... args[]){
    // method body
}

Answer 1

The "Three Dots" in java is called the Variable Arguments or varargs. It allows the method to accept zero or multiple arguments. Varargs are very helpful if you don't know how many arguments you will have to pass in the method.

For Example:

abc(); // Likely useless, but possible 
abc("x", "y", "z"); 
abc("xyz"); 
abc(new String[]{"x", "y", "z"});

But one thing you must not is, the argument that gets the ... must be the last in the method signature. In simpler terms, 

abc (int i, String... strings) is correct, whereas:

abc(String... strings, int i) is wrong.

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Thanks

Comments

Simple and superb answer. Thanks

Answer 2

The three dots (...) are used in a function’s declaration as a parameter. These dots allow zero to multiple arguments to be passed when the function is called. The three dots are also known as var args.

Answer 3

It means that zero or more String objects (or a single array of them) may be passed as the argument(s) for that method.

See the "Arbitrary Number of Arguments" section here: http://java.sun.com/docs/books/tutorial/java/javaOO/arguments.html#varargs

In your example, you could call it as any of the following:

myMethod(); // Likely useless, but possible
myMethod("one", "two", "three");
myMethod("solo");
myMethod(new String[]{"a", "b", "c"});

Important Note: The argument(s) passed in this way is always an array - even if there's just one. Make sure you treat it that way in the method body.

Important Note 2: The argument that gets the ... must be the last in the method signature. So, myMethod(int i, String... strings) is okay, but myMethod(String... strings, int i) is not okay.