Final Chaining

Question

Hey,
I'm messing about with chaining instance-scoped final variables together with deferred execution;
e.g.
public final class FinalChain {
    private final double a;
    private final double b = this.a * 3;
    FinalChain(final double a) {
        this.a = a;
    public String toString() {
        return "" + b;
    public static void main(String[] args ) {
        System.out.println( new FinalChain(3) );
}However, it prints out 0.0 and not 9. Is what I'm trying to do possible and if so, how?
Cheers

Answer 1

Its an ok book, its not great.
The latter half was quite good - but I have learnt that the book is riddled with mistakes.
(have a look at the reviews at amazon for more on this)
As for my code-bug, go and re-read again (in my copy page 53 - "Chapter 2: Deferred Initialisation : Chained deferred initialisation"), 1 the example they give just straight doesn't compile, 2 if u make it so it does compile,
public class FC2 {
    public final String name;
    public final int nameLen = this.name.length();
    public FC2(final String name) {
        this.name = name;
        System.out.println(nameLen);
    public static void main(String[] args) {
        new FC2("hello");
        new FC2("world");
}u get a lovely run-time error.
Exception in thread "main" java.lang.NullPointerException
        at FC2.<init>(FC2.java:5)
        at FC2.main(FC2.java:15)