Functions

Function is a code block that executes certain task.

Syntax

funcType funcName(args) { // Code to execute. }

Void Example

A void function doesn't return any value.

Example:

public class Main { public static void main(String[] args) { // Calling a function: printHi(); } static void printHi() { System.out.print("Hi!"); } }

Output:

Hi!

Returning Result

Via the return keyword a result can be returned.

Let's have an example in which rectangle's area is calculated by passing arguments about it's sides.

Example:

public class Main { public static void main(String[] args) { double area = calcRectangleArea(3, 4); System.out.print(area); } static double calcRectangleArea(double widthArg, double heightArg) { return widthArg * heightArg; } }

Output:

12

There are couple of things to mark:

• A functions is defined at lines 7 - 9. It accepts two arguments - widthArg and heightArg both of type double.
• The function calcRectangleArea returns a double result.
• calcRectangleArea is called at line 3.
• It's returned value is set in the variable area.

Common Exceptions

Return Mismatch

If a function returns value different than the specified type, it causes an exception.

static string returnName() { return 5; // Causes exception. }

In this case 5 should be replaced with string value.

Arguments Type Mismatch

public class Main { public static void main(String[] args) { functionName("John"); // causes exception } static int functionName(int arg) { return 5; } }

Atline 6 the function expects argument of type int.

At line 3 an argument of string type is passed.

The passed argument at line 3 should be replaced with integer value.

Arguments Count Mismatch

public class Main { public static void main(String[] args) { calcTrapezoidArea(3,4); // causes exception } static double calcTrapezoidArea(double a, double b, double h) { return (a + b) / 2 * h; } }

The function calcTrapezoidArea expects 3 arguments but only 2 are passed to it.