Public class variable fields do not respect the encapsulation principle and has two main disadvantages:

• Additional behavior such as validation cannot be added.
• The internal representation is exposed, and cannot be changed afterwards.

The following code:

public class MyClass {

  public static final int SOME_CONSTANT = 0;     // Compliant - constants are not checked

  public String firstName;                       // Non-Compliant

}

should be refactored into:

public class MyClass {

  public static final int SOME_CONSTANT = 0;     // Compliant - constants are not checked

  private String firstName;                      // Compliant

  public String getFirstName() {
    return firstName;
  }

  public void setFirstName(String firstName) {
    this.firstName = firstName;
  }

}