The main method should be as short as
possible
The main method should declare
needed variables and call methods to do the work
Calling a method from the main method
Ø Use the name
Ø If something is returned then assign it to a variable. For example, the following line of code will call a method (note the () which signifies
a method
as opposed to a variable) and assign the returned value to the variable amount amount = figureIt()
Ø The return type must be declared in the method header
public static void figureIt()
{
}
Ø void means the method does not return anything
Ø int means the method returns an integer
Ø float means the method returns a float
public class UsingMethods
{
public static void main(String[] args)
{
int num1 = 5;
int num2 = 6;
int sum;
int product;
announcement();
sum = addNumbers(num1, num2);
product = multiplyNumbers(num1, num2);
giveResults(sum, product);
}
static void announcement()
{
System.out.println("Welcome to the sophisticated math progam");
}
static int addNumbers(int x, int y)
{
int theSum = x + y;
return theSum;
}
static int multiplyNumbers(int a, int b)
{
int theProduct = a*b;
return theProduct;
}
static void giveResults(int y, int z)
{
System.out.println("The sum is: " + y);
System.out.println("The product is: " + z);
}
}
Output
Welcome to the sophisticated math progam
The sum is: 11
The product is: 30
import javax.swing.*;
class Methods
{
public static void main(String[ ] args)
{
double convertedAmount;
String GallonsIn = JOptionPane.showInputDialog("Enter amount in gallons");
double gallons = Double.parseDouble(GallonsIn);
convertedAmount = gallons*3.785;
JOptionPane.showMessageDialog(null,"The amount in liters
is"+convertedAmount,"Conversions",JOptionPane.PLAIN_MESSAGE);
}
Example 1
import javax.swing.*;
class Methods
{
public static void main(String[ ] args)
{
double convertedAmount;
String GallonsIn = JOptionPane.showInputDialog("Enter amount in gallons");
double gallons = Double.parseDouble(GallonsIn);
convertedAmount = toLiters (gallons);
JOptionPane.showMessageDialog(null,"The amount in liters
is"+convertedAmount,"Conversions",JOptionPane.PLAIN_MESSAGE);
}
public static double toLiters(double amount) //note the use of static
{
return amount * 3.785;
}
}
 |
 |
Example 2
import
javax.swing.*;public
class Charing{
public static void main(String[ ] args)
{
double convertedAmount;
String GallonsIn = JOptionPane.showInputDialog("Enter amount in gallons");
double gallons = Double.parseDouble(GallonsIn); char response = toLiters (gallons);
JOptionPane.showMessageDialog(null,"Answer is " + response, "Title", JOptionPane.PLAIN_MESSAGE);
}
public static char toLiters(double amount) //note the use of static
{
if (amount>0)
return 'y';
else
return 'n';}
}