Encapsulation is a more useful fundamental OOP concept. The other three are inheritance, polymorphism, and abstraction. Encapsulation in Java is data variables and methods together as a single unit. In encapsulation, the variables of a class will be hidden from other classes, and can be accessed only through the methods of their current class. Therefore, it is also known as data hiding.
- Declare the variables of a class as private.
- Provide public setter and getter methods to modify and view the variables values.
Example:
/* File name : EncapTest.java */
public class EncapTest {
private String name;
private String idNum;
private int age;
public int getAge() {
return age;
}
public String getName() {
return name;
}
public String getIdNum() {
return idNum;
}
public void setAge( int newAge) {
age = newAge;
}
public void setName(String newName) {
name = newName;
}
public void setIdNum( String newId) {
idNum = newId;
}
}
The public setXXX() and getXXX() methods are the access points of the instance variables of the EncapTest class:
/* File name : RunEncap.java */
public class RunEncap {
public static void main(String args[]) {
EncapTest encap = new EncapTest();
encap.setName("Sophie");
encap.setAge(28);
encap.setIdNum("12343ms");
System.out.print("Name : " + encap.getName() + " Age : " + encap.getAge());
}
}
Output Name
James Age : 20