CODEWITHSUNDEEP
javaoopencapsulation
Sanchit
Sanchit

Reputation: 851

How to restrict another class to alter the properties in java

According to Encapsulation fields should be private and public getter-setters.

But using setter there is a way that another class can alter the value of private field, So what should be the way to protect fields.

Please consider this class for discussion : 

    class Emp {

    private String name;
    private int age;

    public Emp() {}

    // getters and setters

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

Upvotes: 1

Views: 735

Answers (4)

Stephen C
Stephen C

Reputation: 718758

If you don't want other classes to be able to change a field via a setter, simply don't provide the setter. Declaring the setter as private has the same effect.

You said:

According to Encapsulation fields should be private and public getter-setters.

Actually, the key requirement for achieving encapsulation is to declare the fields as private. That is what prevents other classes from "seeing" or depending on how the property is implemented. Providing getters and/or setters is optional.

Upvotes: 2

user7286728
user7286728

Reputation:

You could make the class immutable.

An immutable object is one that will not change state after it is instantiated.

final class Emp {

    private final String name;
    private final int age;

    public Emp(String name, int age) {
        this.name = name;
        this.age = age; 
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

}

Making the class final ensures this class can not be subclassed. This subclass could potentially add mutability.

Upvotes: 4

wake-0
wake-0

Reputation: 3968

When you need the setters add some kind of control:

public void setName(String name) {
    if (name == null) {
        throw new IllegalArgumentException();
    }
    this.name = name;
}

When you use java beans it is also possible to use roles:

@RolesAllowed("Administrator")
public void setName(String nam) {
    ...
}

Upvotes: 0

Orest Savchak
Orest Savchak

Reputation: 4569

Pass data in constructors:

   class Emp {

    private String name;
    private int age;

    public Emp(String name, int age) {
      this.name = name;
      this.age = age;
    }

    // getters

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}

Upvotes: 0

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