Variable length arguments

on

 varargs

In Java, variable-length arguments (varargs) allow a method to accept zero or more arguments of a specified type. This can be very useful when you don't know beforehand how many arguments a method needs to handle.

How to Use Variable-Length Arguments

To declare a varargs parameter in a method, you use an ellipsis (...) after the type of the arguments. Here’s a basic example:

public class VarArgs {
    // Method with varargs to add numbers
    void add(int... num) {
        int sum = 0;
        for (int x : num) {
            sum += x;
        }
        System.out.println(sum);
    }

    public static void main(String[] args) {
        VarArgs obj = new VarArgs();

        // Calling the add method with different numbers of arguments
        obj.add(10, 20);         // Output: 30
        obj.add(10, 20, 30);     // Output: 60
        obj.add(10, 20, 30,40);  // Output: 100
    }
}

Why Use Varargs?

  1. Convenience: Varargs make it easier to write methods that need to accept a flexible number of arguments. You don’t need to overload the method with different versions for different numbers of parameters.

  2. Readability: Code that calls methods with varargs can be more readable because it doesn't need to construct an array explicitly.

  3. Flexibility: Varargs allow you to handle a varying number of arguments in a single method.

Rules and Limitations

  • Only One Varargs Parameter: A method can have only one varargs parameter, and it must be the last parameter in the method’s parameter list. For example: 
                            public void exampleMethod(String s, int... numbers) { ... }
                            This is correct, but this is not:
                            public void exampleMethod(int... numbers, String s) { ... }
  •  Using Varargs: Inside the method, the varargs parameter is treated as an array. You can use it as you would any other array.



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