What are Access Modifiers?

Have you ever wanted to define how people would access some of your properties? You would not want anyone using your underwear. However, your close friends and relatives can use your sweater and maybe your car.

Similarly to how you set a level of access to your posessions, Java controls access, too. You want to define the access level for variables, methods and classes depending on which other classes you want accessing them.

Java provides 4 levels of access modifiers. This means that you can modify access to a variable, method or a class in 4 ways. These 4 ways are private, public, protected and default.

These access modifiers can be applied to fields, methods and classes (Classes are a special case, we will look at them at the end of this artice). Here is a quick overview¹ of what the Access Levels are for each Access Modifier:

Access Modifiers Table Reference:

Private Access Modifier

Allows a variable or method to only be accessed in the class in which it was created. No other class beyond the class that created the variable or method can access it. This is closely similar to your internal organs. They are only accessible to the owner. To make a variable or method private, you simply append the private keyword before the variable or method type. Let us use private in a coding example. If a bank wants to provide an interest rate of 10% on it’s loans, it would make sure that the interest rate variable(let us suppose int int_rate;) would stay private so as no other class would try to access it and change it. For example;

private String name;
The above example creates a variable called name and ensures that it is only accessible within the class from which it was created.

Another example for a method is

private void setAge(){
System.out.println("Set Age");
}

The above example ensures that the method setAge is accessible only within the class from which it was created and nowhere else.

Public Access Modifier

The public access modifier is the direct opposite of the private access modifier. A class, method or variable can be declared as public and it means that it is accessible from any class. Public access modifier can be likened to a public school where anyone can seek admission and be admitted.

A public class, method, or variable can be accessed from any other class at any time.

For example, to declare a class as public, all you need is:

public class Animal{

}

As such, the Animal class can be accessed by any other class.

public int age;
public int getAge(){
}

Above are ways of specifying a variable and a method as public.

The Default Access Modifier

The default access modifier is different from all the other access modifiers in that it has no keyword. To use the default access modifier, you simply use none of the other access modifiers and that simply means you are using a default access modifier.

For example, to use the default access modifier for a class, you use

class Bird{
}

This basically means you are using the default access modifier. The default access modifier allows a variable, method, or class to be accessible by other classes within the same package. A package is a collection of related classes in a file directory. For more information about packages, check out the section on packages.

Any variable, method, or class declared to use the default access modifier cannot be accessed by any other class outside of the package from which it was declared.

int age;
void setNewAge(){
}

Above are some ways of using the default access modifier for a variable or method. Don’t forget, the default access modifier does not have a key word. The absence of the 3 other access modifiers means you are using the default access modifier.

Protected Access Modifier

The protected access modifier is closely related to the default access modifier. The protected access modifier has the properties of the default access modifier but with a little improvement.

A variable and method are the only ones to use the protected access modifier. The little improvement is that a class outside the class package from which the variable or method was declared can access the said variable or method. This is possible ONLY if it inherits from the Class, however.

The class from another package which can see protected variables or methods must have extended the Class that created the variables or methods.

Note without the advantage of Inheritance, a default access modifier has exactly the same access as a protected access modifier.

Examples of using the protected access modifier is shown below:

protected int age;
protected String getName(){
  return "My Name is You";
}

Access Modifiers on Classes

By default, classes can only have 2 modifiers:

• public
• no modifier (default modifier)

So this means classes can never be set to private or protected?

This is logical, why would you want to make a private class? No other class would be able to use it. But sometimes, you can embed a class into another class. These special classes, inner classes, can be set to private or protected so that only its surrounding class can access it:

public class Car {
    private String brand;
    private Engine engine;
    // ...    
    private class Engine {
        // ...
    }
}

In the above example, only the Car class can use the Engineclass. This can be useful in some cases.

Other classes can never be set to protected or private, because it makes no sense. The protectedaccess modifier is used to make things package-private but with the option to be accessible to subclasses. There is no concept such as ‘subpackages’ or ‘package-inheritance’ in java.