Implementing a Builder Pattern (Not Necessarily Gof)

Question

What I am looking for is some examples (ref. Joshua Bloch's Builder) on a plain java object such that:
// has a min. set of required properties and I can
// add any number of optional properties and then
// call a single build method to return me an instance
// of type Message
class Message {
private int id;
private String title;
private String author;
// optional
private String summary;
private double txCost;
public Message(int id, String titile, String author) {
// normal this.id = id , etc...
public Message summary(String summary) {
public Message txCost(double txCost) {
public Message build() {
// this actually returns the new instance with min and opt params
// Message m = Message(1, "Title","dk").summary("summa").build();
Thanks

Answer 1

I agree with dubwai that you wouldn't implement a build method in the class you have already created, that returns another instance of itself
I also don't think you should preface your request with "not necessarily GoF". I think J.B. was definitely suggesting a good application of the GoF builder pattern in order to make immutable objects elegant and relatively easier to deal with.
In the end, you are trying to satisfy at least 2 things. (I'm sure there are others)
1. Turn a mutable POJO into an immutable object.
2. Provide an elegant creation mechanism for initializing the object without having long winded, and type ambiguous construction.
Your example doesn't necessarily require the addition of a builder to make your Message immutable, but let me provide you the example anyway.
// has a min. set of required properties and I can
// add any number of optional properties and then
// call a single build method to return me an instance
// of type Message
public class Message {
    // make these properties "final". This makes them immutable
    private final int id;
    private final String title;
    private final String author;
// optional
   private final String summary;
   private final Double txCost; /*convert to immutable wrapper, allows simulation of
                                                       "optional", i.e. null means wasn't used in initialization */
/* cannot construct a message without the use of a builder */
private Message(Builder builder) {
     this.id = builder.id;
     this.title = builder.title;
     this.author = builder.author;
     this.summary = builder.summary;
     this.txCost = builder.txCost;
// normal this.id = id , etc...
// getters for properties
// end getters
   /* Note, the Builder is a static inner class, it is only relevant for creating instances of
      Message.
   public static class Builder{
    // short lived mutables
         private int id;
         private String title;
         private String author;
        private String summary;
        private Double txCost;
        /* you cannot have a Message without these required fields, so we force them
          in the constructor */
        public Builder(int id, String title, String author){
            this.id = id;
            this.title = title;
            this.author = author;
        /* I prefer the setter names, but the Builder behavior of returning the this object */
        public Builder setSummary(String summary){
            this.summary = summary;
            return this;
        public Builder setTxCost(double txCost){
             this.txCost = txCost; // note Java 1.5 autoboxing/unboxing
             return this;
        public Message build() {
             return new Message(this);
} Now you can create four different permutations of Message
Message basic = new Message.Builder(1,"A MIDSUMMER NIGHT'S DREAM", "WILLIAM SHAKESPEAR").build();
Message summary = new Message.Builder(2, "SOLARIS","STANISLAW LEM").setSummary("Great Sci-Fi book, bad movie").build();
Message txCosted = new Message.Builder(3, "FIGHT CLUB","CHUCK PALINIUK").setTxCost(30,000,000.00).build();
Message all = new Message.Builder(4, "BUILDER","DANIEL SHAW").setSummary("Check out the builder eclipse plug-in at sourceforge").setTxCost(0.0).build(); //Shameless self promotion