effective-java

I am reading the Effective Java by Joshua Bloch and I have question about Item1 Static Factory Method . Quote[Bloch, p.7] Interfaces cant have static methods, so by convention, static factory methods for an interface named Type are put in non-instantiable class named Types. For example, the Java Collections Framework, provide unmodifiable collections, synchronized collections, and the like. Nearly all of these implementations are export via static factory methods in one noninstantiable class (java.util.Collections). The classes of the returned objects are all non-public. Ok. When look at the

Lovely equals and hashcode, all the theory is here and also here I have taken the decision to use the auto-generated id within equals() and hashcode() in a number of my hibernate entity/domain objects. However, a number of websites say you should never do this due to the risk of persisting an object to the database for the first time whilst it is in the process of being compared or using hashcode. My point of view is that in most use cases this is much more unlikely than any other field being changed. The individual domain objects have the id generated once when they are first created, whereas

What is the difference between compile time and run time type of any object in Java ? I am reading Effective Java book and Joshua Bloch mentions about compile time type and run time types of array instances in Item 26 many times mainly to describe that suppressing cast warnings can be safe sometimes. // Appropriate suppression of unchecked warning public E pop() { if (size == 0) throw new EmptyStackException(); // push requires elements to be of type E, so cast is correct @SuppressWarnings("unchecked") E result = (E) elements[--size]; elements[size] = null; // Eliminate obsolete reference

I am reading the chapter on Serialization in Effective Java . Who calls the readObject() and writeObject()? Why are these methods declared private ? The below is a piece of code from the book // StringList with a reasonable custom serialized form public final class StringList implements Serializable { private transient int size = 0; private transient Entry head = null; //Other code private void writeObject(ObjectOutputStream s) throws IOException { s.defaultWriteObject(); s.writeInt(size); // Write out all elements in the proper order. for (Entry e = head; e != null; e = e.next) s.writeObject

I am reading the chapter on Generics in Effective Java. Help me understand difference between Set , Set<?> and Set<Object> ? The following paragraph is taken from the book. As a quick review, Set<Object> is a parameterized type representing a set that can contain objects of any type, Set<?> is a wildcard type representing a set that can contain only objects of some unknown type, and Set is a raw type, which opts out of the generic type system. What is meant by "some unknown type"? Are all unknown types of type Object ? In that case what is the specific difference between Set<?> and Set<Object>