Ankit Garg

As Arun said it is not necessary to make the instance field final in singleton class. If you want to lazy initialize the class you can initialize it in the getInstance method. The example you gave where another method is making the instance null again, if there is such a code then your class will no longer be singleton. But that's a programming mistake (or design flaw or logical fault whatever), even making the instance final won't help if you make a programming mistake like that. For example this class will always create a new instance as the code is logically wrong:

class BadSingleton {   // final instance   private static final BadSingleton instance = new BadSingleton();   public static BadSingleton getInstance() {      // always returning a new instance      BadSingleton instance = new BadSingleton();      return instance;   } }

I don't think for the exam you'll need to know syntax of JDBC connection for Oracle (even though Oracle controls the certification )

Although this is old, but on Java 6 or before since the pool was in PermGen, so following code results in false as the intern method call creates a new String in PermGen and s0 and s1 refer to different String objects:

String s0 = "hello ".concat("world"); String s1 = s0.intern();         System.out.printf("s0==s1 : %b\n", s0 == s1);

Welcome Cay. I loved your Core Java Vol I & II (I had the 7th Edition) and I'm going through the Scala for the Impatient and loving it as well

If you just want to print the output on console then use Arrays.toString...

That's a good point. \b matches boundary at the start of the String also. So my guess is even if the space before 2 is matched in the previous match (with \D), \b can consider 2 to be start of a String and match it as a word boundary...

In the example add/offer method is not blocking. Only the transfer method is blocking because that's its purpose. This is what the documentation of the method says:

javadoc wrote:Transfers the element to a consumer, waiting if necessary to do so.
More precisely, transfers the specified element immediately if there exists a consumer already waiting to receive it (in take() or timed poll), else inserts the specified element at the tail of this queue and waits until the element is received by a consumer.

If you split by non-whitespace character, why would it split by the spaces? It would split by all characters which are not spaces. So it would split for each non-space character. By that theory the count is lesser and that's because split method removes all trailing empty elements. If you print the tokens array you'll see that it is generating blank tokens (and tokens with spaces)...

I don't have the book at hand, but are you sure the example says the add/offer methods are blocked/throws exception?

Hi Johnny, welcome to JavaRanch.

Many mock exams cover stuff which is not covered in the exam. They probably do it probably to make it difficult so that you think it is the best mock exam

Best resource to check what is or is not on the exam is to check exam objectives. But if you come across any question which is not covered in the book, the extra knowledge won't hurt so probably briefly reading about the topic should be good for knowledge (if not the exam)...

From what I've seen in my career so far, even with single page applications the login page is separate. That way you don't send all your client logic to any unauthorized user. Once user is logged in, the user is sent to the single page application which has all the functionality. So IMO you should go with the first approach instead of Kendo showing a login page. But that's just my opinion on the matter

Proxy pattern may or may not be used in AOP, it depends on the implementation but yes for Spring it is used. Same goes for singletons, Spring beans may or may not be singletons and spring beans being singleton has nothing to do with AOP. You can even say that AOP is like Decorator design pattern. But more than design patterns, AOP is about the issues it solves. It gives you a way to handle cross cutting concerns...

Hi Shahana, I think you are thinking of regex incorrectly. The entire pattern is matched multiple times. So the first time "\\b\\w+\\D\\b" matches "OCPJP ", then next time it matches "2013 ". The next time it didn't match because OCPJP7 had a number in the end which didn't match \D and there was no space at the end. "2013 " matched because \D matched the space after 2013...

Agreed, if this is not mentioned it should be mentioned. Also you cannot declare all type of final variables, it needs to be a compile time constant so it is limited to String and primitive types. So if you try to do this it will not compile:

class Outer {   class Inner {       public static final Object obj = null;   } }

I'm assuming you've modified the code to make the methods and fields static. Singleton is more powerful than using a class with everything static in some cases:

Polymorphism: Since the singleton is an instance, you can use the instance as a regular object. So you can pass it to other methods which is especially useful if your singleton class implements an interface.

Lazy Loading: If the singleton object is heavy, you can lazy load it inside the getInstance method...