Constructor initalization lists

Question

I come from C++ and wonder how I can initialize members of subclasses before calling the parent constructor:
e.g.
class MyParent {
  int a;
  public MyParent(int a) {
    this.a=a
    initSomeStuff();
  protected void additionalnitialization() {
class MyClass extends MyParent {
  int b;
  int c;
  public MyClass(int a, int b) {
    super(a); // I must call this first!
    this.b = b;
  @Override
  protected void additionalnitialization() {
    // when this function is called a is NOT initialized yet!
    c = a+b;
}How can I initialize b before calling the super constructor?
In C++ i would use initialization lists like this (pseudo-code):
class MyClass extends MyParent {
  int b;
  int c;
  public MyClass(int a, int b) : this.b(b) {
    super(a); // at this time b is already initialized through the initalization list
}what is the java-way to do this?
Edited by: java-noob-from-cpp on Feb 9, 2009 1:57 PM

Answer 1

so what do you java-guys use to workaround this?
I'll try to provide a better example, wher I would like to use this kind of functionality: from the last posts I already know, that this won't work, but I hope that this example could clarify this.
I have one parent widget that has a lot of common functionality and it just wants to allow it's children to provide one distinct widget.
abstract class BloatedParent {
  someParams;
  public BloatedParent(someParams) {
    this.someParams = someParams;
    createWidgets();
    layoutWidgets();
  private createWidget() {
    Container container = new Container();
    container.add(new Toolbar);
    // I should NOT do this in java, I know: but what else?
    container.add(getCustomWidgetFromChild());
    container.add(..);  
  protected abstract Widget getCustomWidgetFromChild();
class Child1 extends BloatedParent {
   Object1 object1;
   Child1(someParams, object1) {
     super(someParams);
     this.object1 = object1;
   protected Widget getCustomWidgetFromChild() {
      // e.g. build some fancy Panel Widget and return it
      // will of course NOT work, because this.object1 is not assigned yet
      return new FancyPanel(object1.getTitle(), object1.getName(),  ..);
class Child2 extends BloatedParent {
   Object2 object2;
   Child2(someParams, object2) {
     super(someParams);
     this.object2 = object2;
   protected Widget getCustomWidgetFromChild() {
      // e.g. build a nice Image Widget
      // will also NOT work...
      return new NiceImage(object2.getFilename(), object2.getHeight(),  ..);
}what I could do of course, is to move all function calls from the constructor to a method called initialize() and then every child just had to call this method, after it has set its constructor args, like this:
abstract class BloatedParent {
  someParams;
  public BloatedParent(someParams) {
    this.someParams = someParams;
  // children MUST call this at the end of their constructors!
  protected initialize() {
     createWidgets();
     layoutWidgets();
class Child1 extends BloatedParent {
   Object1 object1;
   Child1(someParams, object1) {
     super(someParams);
     this.object1 = object1;
     initialize();
}but that just feels sooo wrong