Core Java Interview Questions

1) Explain about Core Java ?

 Java is increasingly used for middleware applications to communicate between Server and clients. Java has features such as multithreading, portability and networking capabilities. Changes in the java library made java as a favorite programming language for developers it added functionality to their scripts.

2) State some advantages of Java?

 Platform independence is the key feature of Java during runtime. Syntax of java is similar to the popular object oriented languages such as C and C++. Java program can eliminate most of the bugs present in the program. Manual memory allocation and de allocation feature present in Java is automated.

3) State the main difference between C++ and Java?

 The main difference between C++ and Java lies in multiple inheritances. Java Meta class model has a better solution than C++. Persistent objects can be implemented by features such as object serialization and reflection mechanism. GUI can be implemented easily.

4) Explain about the security aspect of Java?

 Java has some bugs in its applets. Java team stated that they have zero tolerance over security features and subsequent editions of Java are improving Bug free environment. Some of the features are overriding the runtime stack, disallowing the corruption of memory outside its own process, reading or writing on local files where it is actually forbidden to do these processes, etc.

5) Explain about the interpreter in Java?

 Machines should have Java interpreter for the Java byte code to get executed. Linking is a very easy process and this feature helps while developing applications. Java compiler which is available with software development kit is a bit slower in execution of scripts.

6) Explain about the performance aspects of Core Java?

 Performance of interpreted byte codes is enough but it can be improved much more than that. Byte codes are translated into machine language within no time, this speed of execution can be achieved during application compiling time. JIT compilers are also present which compile the byte codes into native code.

7) Explain about the dynamic behavior of core java?

 This language was designed to adapt the changing environment and behavior. New methods and instance variables can be added to the client side without any major changes happening at the client end. This function is very important for GUI builders, pluggable components, debuggers and object database.

8.)Explain about Java SDK?

 Java SDK is not so comfortable with people used to command line interpreter. IDEs include compilers, editors, debugging facilities, drag and drop techniques, etc. This compiler strives to generate hundreds of lines in code UI. This platform may become a universal platform.

9) What are the three best choices for development environment?

 The three best choices for development environment include.

 1) Java SDK and text editor can be a perfect choice.

 2) Java SDK and a text editor which is built within the SDK.

 3) Using IDE such as free Forte community edition.

10) Explain about Class in Java?

 In Java every thing exists within a class. It defines the behavior of the class and its characteristics. Java applications and applets are built in the class. Rules present for class name are generous and some of the basic rules are names should start with a letter after that letter they can have any combination of letters and digits. It can contain names to any length.

 11) Explain about data types?

 Variables declared should have a declared type. Out of the eight data types four data types are integer, two are floating type integers, one is character type out of which one is Boolean and the other Unicode. Core Java is known to be a strong typed language.

12) Explain about assignment statement?

 After declaring a variable, it should be initialized explicitly. Uninitialized variable can never be used. To a declared variable you must assign a variable name on the left, equal sign and a java expression should have a appropriate value to the right.

13) Give the difference between the println method and sqrt method?

 Println method operates on the object system.out and has the value which should be printed namely y. sqrt method is a static method. It does not operate on any object. It has the number stored in x for which the square toot should be found out.

14) Explain about strings in Java?

 Strings represent nothing but a string of characters. Java does not have any built in string type. It contains predefined class which can be called enough as a String. Instance of a string is called as a string. Much similar to many object oriented languages a + sign is used.

15) Explain the reason behind ending a program with a System.exit (0)?

 The reason behind ending a program with System.exit (0) involves technicalities. When main method exits the new thread automatically does not end. The appearance of this thread is because of dialog box functionality. System.exit ends all the methods.

16) Explain about inheritance hierarchies?

 An inheritance hierarchy has a collection of all classes which fall under the main class. Inheritance chain defines the path from where all the sub classes originated and their relation ship. Controller normally handles user input. Inheritance hierarchy is very important in software modeling.

17) Explain about the select method with an example?

 Select part is useful in selecting text or part of the text. Arguments specified for the select command are the same as applicable to substring. First index is usually represents the start of the index. End of line makers are counted as one character.