V6052. Calling an overridden method in parent-class constructor may lead to use of uninitialized data.


The analyzer has detected a parent-class constructor that uses a method overridden in the derived class. As a result, the overridden method can be used by uninitialized class fields.

This behavior occurs when you fail to follow the class initialization procedure stated in JLS [12.5].

Consider the following example:

public class Parent {
  private String parentStr = "Black";

  public Parent () {
    printInfo();
  }

  public void printInfo () {
    System.out.println("Parent::printInfo");
    System.out.println("parentStr: " + parentStr);
    System.out.println("-----------------");
  }
  ....
}

public class Child extends Parent {
  private int childInt;
  private String childStr;

  public Child() {
    super();
    this.childInt = 25;
    this.childStr = "White";
  }

  public void printInfo () {
    super.printInfo();
    System.out.println("Child::printInfo");
    System.out.println("childInt: "+childInt+";childStr: "+childStr);
    System.out.println("-----------------");
  }
  ....
}

If we execute the following line:

Child obj = new Child();

the program will print:

Parent::printInfo
parentStr: Black
-----------------
Child::printInfo
childInt: 0 ; childStr: null
-----------------

As seen from this fragment, the overridden method 'printInfo' was called in the parent-class constructor of the 'Parent' class, while the derived 'Child' class was not fully initialized – hence the default values, rather than user-specified values, of the 'childInt' and 'childStr' fields.

The conclusion is this: make sure your parent-class constructors do not use methods that could be overridden in child classes. And if you do use a class method in a constructor, declare it final or private.


Bugs Found

Checked Projects
367
Collected Errors
13 552