Creating your own methods

Intermediate Java

Jim White

Java Developer

Why we use methods

Great for repeated tasks
Reusing of code
Avoid repetition (and potential mistakes)
Easier to update and fix mistakes
Don't Repeat Yourself (DRY)

How to define methods

returnType methodName(){

  // Code to be run

}

void method

Only performs an action, doesn't return anything
void means nothing

void sayHello(){
    System.out.println("Hello there!");
  }

Method that produces result

Methods can produce a result
- To store, to use later, to pass to another part of our program, ...
- E.g., method that calculates square of a number
Need to:
- Use specific return type like int or String
- Include return statement

int getSquare() {
  return 5 * 5
}

Naming convention

Lower camel case

First letter lowercase, additional words start with capital letter
Examples:
- getSquare()
- sayHello()

Case sensitivity

Java is case sensitive!

If method is called getSquare(), getsquare() won't work!

Built-in vs. Custom methods

Built-in

Called using the dot notation
- "JAVA".toLowerCase();

Custom methods

Called as-is
- sayHello();

Using a custom method

Code showing the sayHello method defined outside of the main method, with the static keyword emphasized

"Hello there!"

Recap

class HelloMethod {
    public static void main (String[] args) {
        sayHello();
        int fiveSquared = getSquare(); // Saving the result of getSquare() as int
    }
    static void sayHello() { // Just prints a message
      System.out.println("Hello there!");
    }
    static int getSquare() { // Returns int 
      return 5*5; 
    }
}

Hello there!

Let's practice!

Intermediate Java