1. What is Hierarchy in java?
In Hierarchy the commonalties are organized into a tree-structured form. at the root, any subtree is found all the attributes and behavior common to all of the descendants of that root.
2. What is polymorphism?
polymorphism captures commonality in algorithms.In Object-Oriented Program design,polymorphism presents a method that can have many forms. polymorphism is related to overloading and overriding.
3. What is an abstract class?
An Abstract class is a class that can only be subclassed. it cannot be Instantiated.
4. What is multiple Inheritance?
Multiple Inheritance has several superclasses and one derived class.
5. What is java?
java is a high level and third-generation programming language.
6. What is JDBC
A general facility interacting with the database.
7. What Is Java 3D?
A Facility for developing applications with 3D graphics.
8. What Is Java Features?
- − Simple
- − Robust
- − Portable
- − interpreted
- − object Oriented
- − distributed
- − Secure
- − platform Independent
- − multithreaded
- − Mobile Software
9. What Java Is not Support?
Pointer and Multiple Inheritance.
10. What Is JVM (JAVA VIRTUAL MACHINE)?
JVM is a platform-independent execution environment that converts Java bytecode into machine language and executes. java was designed to allow application programs to be built that could be run on any platform without having to be rewritten or recompiled by the programmer for each separate platform.
11. How many types of oops principles.
Encapsulation, Inheritance, polymorphism.
12. What Is Use of Bin Lib In JDK?
Bin Containers all tools such as javac, applet viewer, awt tool, etc. whereas Lib Contains All Package And variable.
13. How Many Types Of Data types?
14. What Is An Array?
- An Array Is An object That Stores a list of items.
15. How Do you declare an array?
Array variable indicates the types of object That The Array holds ex:int arr.
16. What is a static variable?
Static variable is shared by all instances of a class.
17. What is meant By Variable?
Variables are locations In memory that can hold values. before assigning any value to a variable it must be declared.
18. Which operators is used to create and concatenate String?
Addtion Operator (+).
19. What Is String ?
A combination of characters is called a string.
20. What is the final variable?
if a variable id declared as a final variable then you can not change its value I become constant.
21. How do we change the values of the elements of the array?
The array subscript expression can be used to change the values of the elements of the array.
22. What is the difference between break and continue?
the break keyword halts the execution of the current loop and forces control out of the loop. the continue is similar to break except that instead of halting the execution of the loop it starts the next iteration.
23. Which keyword is used to inherit a class?
24. What is the difference between superclass & Subclass?
Superclass is a class that is inherited whereas subclass that does the inheriting.
25. What are the advantages of inheritance?
Reusability of code and accessibility of variables and methods of the superclass by the subclass.
26. What restrictions are placed on method overloading?
two methods may not have the same name and arguments list but different return types.
27. What is multithread?
Multiprogramming is the logically concurrent execution of multiple programs. java support multithreaded programming every thread in java is created and controlled by a unique object of the java.lang.Thread class.
28. What is a control statement?
the control statement is used to control the flow of execution of the program and the order of execution depends on the supplied data values and the conditional logic.
29. What is the return statement In java?
It is a special branching statement that transfers the control to the caller of the method this statement is used to return a value to the caller method and terminates the execution of the method.
30. What is a class in java?
A class is a collection of data and methods that operate on that data. the data and method s usually serve to define the content and capabilities of some kind of object.
31. What are constructors?
A constructor is a method that can be accessed anywhere in a program with the same name as the class name and it enables an object to initialize itself when it’s created.
32. What is the use valueOf() method()?
valueOf() method converts data from its internal format into a human-readable form.
33. What are the uses of to LowerCase() and UpperCase() method ?
The method to LowerCase() converts all the characters in a string from uppercase to lowercase. The method to UpperCase() converts all the characters in a string from lowercase to uppercase.
34. What is exception handling in java?
Exception Is a problem that arises in the program during execution. an execution is an event that occurs during the execution of a program. when such an event occurs within a java method, the method creates and exception objects and hands it off the runtime system.