In the previous chapter, we used the term " variable " for x in the example (as shown below).
In Java, variables declared inside a class are called " attributes ".
You can also say that attributes are variables that belong to a class:
Create a class called " Main " with two attributes: x and y :
public class Main {
int x = 5;
int y = 3;
}Another name for attributes is fields .
Accessing Attributes
You can access attributes by creating an object of the class, and by using the dot syntax ( . ):
The following example will create an object of the Main class, with the name myObj . We use the x attribute on the object to print its value:
myObjModify Attributes
You can also modify attribute values
xOr override existing values
xIf you don't want the ability to override existing values, declare the attribute as final :
Example
public class Main {
final
int x = 10;
public static void main(String[] args) {
Main myObj = new Main();
myObj.x = 25; // will generate an error: cannot assign a value to a
final
variable
System.out.println(myObj.x);
}
}The final keyword is useful when you want a variable to always store the same value, like PI (3.14159...).
The final keyword is called a "modifier". You will learn more about these in the Java Modifiers Chapter .
Multiple Objects
If you create multiple objects of one class, you can change the attribute values in one object, without affecting the attribute values in the other:
xMultiple Attributes
You can specify as many attributes as you want:
Example
public class Main {
String fname = "John";
String lname = "Doe";
int age = 24;
public static void main(String[] args) {
Main myObj = new Main();
System.out.println("Name: " + myObj.fname + " " + myObj.lname);
System.out.println("Age: " + myObj.age);
}
}The next chapter will teach you how to create class methods and how to access them with objects.