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:
Example
Create a method inside MyClass:
public
class MyClass {
static void myMethod() {
// code to be executed
}
}
Example Explained
myMethod()is the name of the methodstaticmeans 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.voidmeans 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:
Example
Inside main, call the
myMethod() method:
public
class MyClass {
static void myMethod() {
System.out.println("I just got executed!");
}
public static
void main(String[] args) {
myMethod();
}
}
// Outputs
"I just got executed!"
Run example »
A method can also be called multiple times:
Example
public
class MyClass {
static void myMethod() {
System.out.println("I just got executed!");
}
public static
void main(String[] args) {
myMethod();
myMethod();
myMethod();
}
}
//
I just got executed!
// I just got executed!
// I just got executed!
Run example »
Method Parameters
Information can be passed to functions 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.
The following 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:
Example
public class MyClass {
static void myMethod(String fname) {
System.out.println(fname + " Refsnes");
}
public
static void main(String[] args) {
myMethod("Liam");
myMethod("Jenny");
myMethod("Anja");
}
}
// Liam Refsnes
// Jenny Refsnes
//
Anja Refsnes
Run example »
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
public class MyClass {
static int myMethod(int x) {
return 5 + x;
}
public static void main(String[] args)
{
System.out.println(myMethod(3));
}
}
// Outputs
8 (5 + 3)
Run example »
This example returns the sum of a method's two parameters:
Example
public class MyClass {
static int myMethod(int x, int y) {
return x + y;
}
public static void main(String[] args)
{
System.out.println(myMethod(5, 3));
}
}
// Outputs 8 (5 + 3)
Run example »
You can also store the result in a variable (recommended):
Example
public class MyClass {
static int myMethod(int x, int y) {
return x + y;
}
public static void main(String[] args)
{
int z = myMethod(5, 3);
System.out.println(z);
}
}
// Outputs 8 (5 + 3)
Run example »
A Method with If...Else
It is common to use if...else statements inside methods:
Example
public class MyClass {
// Create a checkAge() method with an
integer variable called age
static void checkAge(int age) {
// If age is less than 18, print "access denied"
if (age < 18) {
System.out.println("Access
denied - You are not old enough!");
// If age
is greater than 18, print "access granted"
} else {
System.out.println("Access granted - You are old enough!");
}
}
public static void main(String[] args) {
checkAge(20); // Call the checkAge method and pass along an age of 20
}
}
// Outputs "Access granted - You are old enough!"
Run example »
