Class methods
Operations on objects in Java are called
methods.
Methods are like math functions: they can take
argumentsand
return a value. On the other hand, methods in Java also
have access to all fields of an object.
To create a method in a class, you must include it in the class. For example, we can define a
print(age) method that will print information about our book and display a warning if the user is not yet old enough for that book.
class Book
{
String name;
String authorName;
int ageRequirement;
String text;
int pageCount;
// create a print method
void print(int age)
{
System.out.< span style="color:#7d9029">println("Name: " +name);
System.out.< span style="color:#7d9029">println("Author: " +authorName);
System.out.< span style="color:#7d9029">println("Number of pages: "+Integer.toString(ageRequirement);
// verification code goes here
}
}
Let's analyze the syntax for creating a method.
1) The first line of a method is its
signature.
2) The return type of the method is written first. Our method does not return any value, so we write
void.
3) Then in the signature is the name of the method (
print).
4) In brackets there is a listing of arguments. Arguments are separated by commas. For each argument, its type and name are specified, separated by a space. In our case, there is only one argument, it has the type
int and the name
age, so there are no commas.
5) After that comes the method code in curly braces. To return a value from a method, write
return <value>;. In the example, the method does not return anything, so
return can be omitted. To prematurely terminate the execution of a method, you can write
return;.
6) In the class itself, we can refer to the fields of the object of this class by name.