Flash cards
Review the key moves
What is the main idea behind Java Encapsulation?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
public ___ Person {Put the learning moves in the order that makes the concept easiest to apply.
Encapsulation
- declare class variables/attributes as private
- provide public get and set methods to access and update the value of a private variable
Get and Set
You learned from the previous chapter that private variables can only be accessed within the same class (an outside class has no access to it). However, it is possible to access them if we provide public get and set methods.
The get method returns the variable value, and the set method sets the value.
Syntax for both is that they start with either get or set , followed by the name of the variable, with the first letter in upper case:
Example
public class Person {
private String name; // private = restricted access
// Getter public String getName() {
return name;
}
// Setter public void setName(String newName) { this.name = newName;
}
}The get method returns the value of the variable name .
The set method takes a parameter ( newName ) and assigns it to the name variable. The this keyword is used to refer to the current object.
However, as the name variable is declared as private , we cannot access it from outside this class:
Example
public class Main {
public static void main(String[] args) {
Person myObj = new Person();
myObj.name = "John"; // error
System.out.println(myObj.name); // error
}
}If the variable was declared as public , we would expect the following output:
However, as we try to access a private variable, we get an error:
Instead, we use the getName() and setName() methods to access and update the variable:
Example
public class Main {
public static void main(String[] args) {
Person myObj = new Person();
myObj.setName("John"); // Set the value of the name variable to "John"
System.out.println(myObj.getName());
}
}
// Outputs "John"Why Encapsulation?
- Better control of class attributes and methods
- Class attributes can be made read-only (if you only use the get method), or write-only (if you only use the set method)
- Flexible: the programmer can change one part of the code without affecting other parts
- Increased security of data