Access Control

Java's access specifiers are public, private, protected and a default access level.

• A public class member can be accessed by any other code.
• A private class member can only be accessed within its class.

Default (without an access modifier)

• A class's fields, methods and the class itself may be default.
• A class's default features are accessible to any class in the same package.
• A default method may be overridden by any subclass that is in the same package as the superclass.

protected

• protected features are more accessible than default features.
• Only variables and methods may be declared protected.
• A protected feature of a class is available to all classes in the same package(like a default).
• Moreover, a protected feature of a class can be available to its subclasses.

Here is an example for a public member variable

public int i;

The following code defines a private member variable and a private member method:

private double j; 
private int myMethod(int a, char b) { // ...

To understand the effects of public and private access, consider the following program:

 
class Test {
  int a;        // default access
  public int b; // public access
  private int c; // private access
  // methods to access c
  void setc(int i) {
    c = i;
  }
  int getc() {
    return c;
  }
}
public class Main {
  public static void main(String args[]) {
    Test ob = new Test();
    ob.a = 1;
    ob.b = 2;
    // This is not OK and will cause an error
    // ob.c = 100; // Error!
    // You must access c through its methods
    ob.setc(100); // OK
    System.out.println("a, b, and c: " + ob.a + " " + ob.b + " " + ob.getc());
  }
}

The output:

a, b, and c: 1 2 100