Working with Methods in Java.pptx

WORKING WITH
METHODS IN JAVA
Computer Programming in Java

At the end of this session, you are expected to:
◦Identify the different parts of a method in Java
◦Identify the different kinds of method
◦Create Java Methods

Java Methods
◦ A method is a block of code which only runs when it is called.
◦ You can pass data, known as parameters, into a method.
◦ Methods are used to perform certain actions, and they are also known as
functions.
◦ Why use methods?
To reuse code: define the code once, and use it many times.

Create a Method
◦A method must be declared within a class.
◦It is defined with the name of the method, followed by
parentheses ().
◦Java provides some pre-defined methods, such as
System.out.println(), but you can also create your own
methods to perform certain actions:

Create a Method (example)
public class MyClass {
static void myMethod() {
// code to be executed
}
}

Example Explained
◦ myMethod() is the name of the method
◦ static means that the method belongs to the MyClass class and not
an object of the MyClass class. You will learn more about objects
and how to access methods through objects later in this tutorial.
◦ void means that this method does not have a return value. You will
learn more about return values later in this chapter

Call a Method
◦To call a method in Java, write the method's name followed
by two parentheses () and a semicolon;
◦In the following example, myMethod() is used to print a
text (the action), when it is called:

Call a Method (Example)
System.out.println("I just got executed!");
}
public static void main(String[] args) {
myMethod();
}
}
// Outputs "I just got executed!"

Call a Method (Example)
System.out.println("I just got executed!");
}
myMethod(); //method call
}
}

Java Method Parameters
◦ Parameters and Arguments
◦ Information can be passed to methods as parameter. Parameters act
as variables inside the method.
◦ Parameters are specified after the method name, inside the
parentheses. You can add as many parameters as you want, just
separate them with a comma.

Java Method Parameters (Example)
static void myMethod(String fname) {
System.out.println(fname + " Refsnes");
}
myMethod("Liam");
myMethod("Jenny");
myMethod("Anja");
}
}
OUTPUT:
Liam Refsnes
Jenny Refsnes
Anja Refsnes
The example has a method that takes a String
called fname as parameter. When the method is
called, we pass along a first name, which is used
inside the method to print the full name:

Argument
◦When a parameter is passed to the method, it is
called an argument.
◦So, from the example above: fname is a parameter,
while Liam, Jenny and Anja are arguments

Multiple Parameters
static void myMethod(String fname, int age) {
System.out.println(fname + " is " + age);
}
myMethod("Liam", 5);
myMethod("Jenny", 8);
myMethod("Anja", 31);
}
}
OUTPUT
Liam is 5
Jenny is 8
Anja is 31
Note that when you are working with multiple parameters,
the method call must have the same number of arguments
as there are parameters, and the arguments must be
passed in the same order.

Return Values
◦The void keyword, used in the examples above, indicates
that the method should not return a value. If you want the
method to return a value, you can use a primitive data type
(such as int, char, etc.) instead of void, and use the return
keyword inside the method:

Example 1 (Single Parameter)
static int myMethod(int x) {
return 5 + x;
}
System.out.println(myMethod(3));
}
}
//
OUTPUT
8

Example 2 (Multiple Parameters)
static int myMethod(int x, int y) {
return x + y;
}
System.out.println(myMethod(5, 3));
}
}
OUTPUT
8

Problem. Save your program as AverageMethod
◦Write a method named computeAverage() that holds two
parameters and computes the average of two numbers and
return the result.
◦Write another method named validateResult() that prints
HIGH if the average is above 50 and LOW, otherwise.

Solution:
public class AverageMethod{
public static void main(String[] args)
{ double average = computeAverage(78, 34);
System.out.println("The average is "+average);
validateResult(average);
}
public static double computeAverage(double num1, double num2)
{
return (num1+num2)/2;
}
public static void validateResult(double average)
{
if(average>50)
System.out.println("HIGH");
else
System.out.println("LOW");
}
}

Working with Methods in Java.pptx

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