Methods in Java

Objectives

• Write and call (use) methods
• Pass arguments to a method
• Return a value from a method
• Understand how calling a method alters execution flow

Prerequisites

• Understand Java primitive types
• Understand execution flow and control statements
  • Sequence
  • Selection (if statement)
  • Repetition (while, for, do while statements)

Writing a Method

• The main reason for writing code inside methods, is to make the code resuable.
• Write code inside methods also helps to organize a program.
• A method consists of a header and a body.
• The header is the first line of the method.
• The body begins and ends with braces.
• Syntax:
  modifiers returnType methodName(parameter1, parameter2, ..., parameterN)
  {
          method body;
  }
• Example:
  public static double average(double a, double b, double c)
{
    double sum;
    sum = a + b + c;
    return sum / 3.0;
}

Calling a Method

• The computer will not execute the code in a method until the method is called.
• To call a method, simply type the method name followed by an argument list to match the method's parameter list.
• Syntax:
  varName = methodName(argument1, argument2, ..., argumentN);
• Examples:
  double avg;
avg = average(3.1, 5.4, 2.3);
double avg2 = average(6, 2, 3);

Complete Example

public class MethodTest
{
	public static void main(String args[])
	{
		double num1 = 4.1;
		double num2 = 4.2;
		double num3 = 5.7;
		double avg = average(num1, num2, num3);
		System.out.println("average is " + avg);
	}

	public static double average(double a, double b, double c)
	{
		double sum;
		sum = a + b + c;
		return sum / 3.0;
	}
}