Java Functions

Functions

• Functions are called to perform some sort of routine

  • This routine could be adding two numbers, printing a statement, whatever you'd like!

• We create functions so that we don't have to rewrite code

• Functions consist of three main parts:

  • A return type, arguments, and a body
    • The return type tells us what type of variable the function will give us (maybe an integer or a string)
    • The arguments are what we can pass to a function (maybe we pass it one integer, maybe two)
    • The body defines what we do with the arguments, and what we return

• E.g. take a look at the following two functions

   	public static int add(int x, int y)
   	{
   		int sum = x + y;
   		return sum;
   	}

  • Here the return type is integer, the arguments are the two integers x and y, and the body of the function adds the two arguments.

• A function could also not return anything. In that case, we say the return type is void

   	private static void print()
   	{
   		System.out.println("Hello World!");
   	}

  • Note that this function has no return type, nor does it take any arguments! It just prints Hello World! to the terminal.

• Finally, to invoke or call these functions, we would do the following

   	int sum = add(5,10);	// here we assign the return value to the variable sum
   	print();		// here we invoke a void function with no arguments