Adapter Design Pattern in Java with Example

Adapter design pattern in Java, also known as the Wrapper pattern is another very useful GOF pattern, which helps to bridge the gap between two classes in Java. As per the list of Gang of Four patterns, Adapter is a structural pattern, much like Proxy, Flyweight, Facade, and Decorator pattern in Java. As the name suggest, Adapter allows two classes of a different interface to work together, without changing any code on either side. You can view Adapter pattern is a central piece of the puzzle, which joins two pieces, which can not be directly joined because of different interfaces. I see a couple of reference of Adapter design pattern in one of my favorite book Clean Code, but the idea is very well explained in Head First Design Pattern, the image which they show to illustrate Adapter design pattern is worth all the talk.

5 Free OCAJP 7 and OCPJP7 Mock Exams - Online Practice Test (1Z0-803 and 1Z0-804

Hello guys, today I am going to share a list of free OCAJP7 and OCPJP7 mock exams and online practice tests. If you are preparing for Java SE 7 Programmer 1 or 2 certification or upgrading your existing OCJP 6 exam then this will help you to gauge your progress. As per my experience, the three keys to success in any Java certification is a selection of good books, writing small Java programs to understand concepts, and practicing mock exams. You can see that mock exams are very important to do well on the real exam. They give you much-needed practice as well as some idea about what kind of questions you can expect on real exams. Unfortunately, there are not many good quality free mock exams available for OCAJP7 but I have managed to collect some of them. Earlier, I have shared some OCAJP8 mock exams and received a lot of feedback from my readers about a similar list for OCAJP7 and OCPJP7 exams. This is a smaller list as compared to the previous one but I'll keep adding new mock exams if I come across.

java.lang.numberformatexception for input string null - Cause and Solution

The java.lang.NumberFormatException comes when you try to parse a non-numeric String to Number e.g. Short, Integer, Float, Double etc. For example, if you try to convert . "null" to an integer then you will get NumberFormatException. The error "Exception in thread "main" java.lang.NumberFormatException: For input string: "null" is specifically saying that the String you receive for parsing is not numeric and it's true, "null" is not numeric. Many Java methods which convert String to numeric type e.g. Integer.parseInt() which convert String to int, Double.parseDoble() which convert String to double, and Long.parseLong() which convert String to long throws NumberFormatException to inform that the input String is not numeric.