More on methods

You have been working with the main method so far. The main method is a special type of method. Every standalone program must have a main method to allow it to be run from the command line using the java executable.

What is a method?

A method is a named block of code that performs a specific task when called. Using methods is a form of procedural abstraction, which allows us to use a method without needing to know the complex details of its implementation.

Program execution jumps to a method when that method's name is invoked (a.k.a. called).

A method call interrupts the program's sequential flow. Control jumps to the called method, executes it, and then returns to the point immediately following the method call. For a detailed explanation, see Unit 1: Method Signatures.

However, all other methods are invoked by the main method or another method from the same or a different class.

Multiple Parameters Example

In the example below, the addTwoNumbers method is defined with two parameters, a and b. This method is invoked by passing the arguments 10 and 16 from the main method.

Task: Defining and invoking a method with multiple parameters.

public class Addition {
   public static void main(String[] args) {
       int sum = addTwoNumbers(10, 16);
       System.out.println("sum is " + sum);
   }
   public static int addTwoNumbers(int a, int b){
       return a + b;
   }
}

Why should you add methods?

Methods help compartmentalize your code. You typically write new methods when:

• The number of statements in a method exceeds 25 or 30. In such cases, you should look for opportunities to extract logical sections into separate methods.
• A block of code repeats across multiple parts of your program. The repeating block should be extracted into a method and replaced with a method invocation.

The steps above are called refactoring your code.

Every good programmer refactors their code multiple times to ensure it is understandable. Your code should read like a story, easily understood by you and any other programmer who reviews it.