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Interview Questions/Answers

Java Q & A

Total Java questions: 107

Q 1) What is the difference between an Interface and an Abstract class?
Q 2) What is the purpose of garbage collection in Java, and when is it used?
Q 3) Describe synchronization in respect to multithreading.
Q 4) Explain different way of using thread?
Q 5) What are pass by reference and passby value?
Q 6) What is HashMap and Map?
Q 7) Difference between HashMap and HashTable?
Q 8) Difference between Vector and ArrayList?
Q 9) Difference between Swing and Awt?
Q 10) What is the difference between a constructor and a method?
Q 11) What is an Iterator?
Q 12) State the significance of public, private, protected, default modifiers both singly and in combination and state the effect of package relationships on declared items qualified by these modifiers.
Q 13) What is an abstract class?
Q 14) What is static in java?
Q 15) What is final?
Q 16) What if the main method is declared as private?
Q 17) What if the static modifier is removed from the signature of the main method?
Q 18) What if I write static public void instead of public static void?
Q 19) What if I do not provide the String array as the argument to the method?
Q 20) What is the first argument of the String array in main method?
Q 21) If I do not provide any arguments on the command line, then the String array of Main method will be empty or null?
Q 22) How can one prove that the array is not null but empty using one line of code?
Q 23) What environment variables do I need to set on my machine in order to be able to run Java programs?
Q 24) Can an application have multiple classes having main method?
Q 25) Can I have multiple main methods in the same class?
Q 26) Do I need to import java.lang package any time? Why?
Q 27) Can I import same package/class twice? Will the JVM load the package twice at runtime?
Q 28) What are Checked and UnChecked Exception?
Q 29) What is Overriding?
Q 30) What are different types of inner classes?
Q 31) Are the imports checked for validity at compile time? e.g. will the code containing an import such as java.lang.ABCD compile?
Q 32) Does importing a package imports the subpackages as well? e.g. Does importing com.MyTest.* also import com.MyTest.UnitTests.*?
Q 33) What is the difference between declaring a variable and defining a variable?
Q 34) What is the default value of an object reference declared as an instance variable?
Q 35) Can a top level class be private or protected?
Q 36) What type of parameter passing does Java support?
Q 37) Primitive data types are passed by reference or pass by value?
Q 38) Objects are passed by value or by reference?
Q 39) How do I serialize an object to a file?
Q 40) Which methods of Serializable interface should I implement?
Q 41) How can I customize the seralization process? i.e. how can one have a control over the serialization process?
Q 42) What is the common usage of serialization?
Q 43) What is Externalizable interface?
Q 44) When you serialize an object, what happens to the object references included in the object?
Q 45) What one should take care of while serializing the object?
Q 46) What happens to the static fields of a class during serialization?
Q 47) Does Java provide any construct to find out the size of an object?
Q 48) What are wrapper classes?
Q 49) Why do we need wrapper classes?
Q 50) What are checked exceptions?
Q 51) What are runtime exceptions?
Q 52) What is the difference between error and an exception?
Q 53) How to create custom exceptions?
Q 54) If I want an object of my class to be thrown as an exception object, what should I do?
Q 55) If my class already extends from some other class what should I do if I want an instance of my class to be thrown as an exception object?
Q 56) How does an exception permeate through the code?
Q 57) What are the different ways to handle exceptions?
Q 58) What is the basic difference between the 2 approaches to exception handling. 1> try catch block and 2> specifying the candidate exceptions in the throws clause? When should you use which approach?
Q 59) Is it necessary that each try block must be followed by a catch block?
Q 60) If I write return at the end of the try block, will the finally block still execute?
Q 61) If I write System.exit (0); at the end of the try block, will the finally block still execute?
Q 62) How are Observer and Observable used?
Q 63) What is synchronization and why is it important?
Q 64) How does Java handle integer overflows and underflows?
Q 65) Does garbage collection guarantee that a program will not run out of memory?
Q 66) What is the difference between preemptive scheduling and time slicing?
Q 67) When a thread is created and started, what is its initial state?
Q 68) What is the purpose of finalization?
Q 69) What is the Locale class?
Q 70) What is the difference between a while statement and a do statement?
Q 71) What is the difference between static and non-static variables?
Q 72) How are this() and super() used with constructors?
Q 73) What are synchronized methods and synchronized statements?
Q 74) What is daemon thread and which method is used to create the daemon thread?
Q 75) Can applets communicate with each other?
Q 76) What are the steps in the JDBC connection?
Q 77) How does a try statement determine which catch clause should be used to handle an exception?
Q 78) Can an unreachable object become reachable again?
Q 79) What method must be implemented by all threads?
Q 80) What are synchronized methods and synchronized statements?
Q 81) What is Externalizable?
Q 82) What modifiers are allowed for methods in an Interface?
Q 83) What are some alternatives to inheritance?
Q 84) What does it mean that a method or field is "static"?
Q 85) What is the difference between preemptive scheduling and time slicing?
Q 86) What is the catch or declare rule for method declarations?
Q 87) Is Empty .java file a valid source file?
Q 88) Can a .java file contain more than one java classes?
Q 89) Is String a primitive data type in Java?
Q 90) Is main a keyword in Java?
Q 91) Is next a keyword in Java?
Q 92) Is delete a keyword in Java?
Q 93) Is exit a keyword in Java?
Q 94) What happens if you dont initialize an instance variable of any of the primitive types in Java?
Q 95) What will be the initial value of an object reference which is defined as an instance variable?
Q 96) What are the different scopes for Java variables?
Q 97) What is the default value of the local variables?
Q 98) How many objects are created in the following piece of code? MyClass c1, c2, c3; c1 = new MyClass (); c3 = new MyClass ();
Q 99) Can a public class MyClass be defined in a source file named YourClass.java?
Q 100) Can main method be declared final?
Q 101) What will be the output of the following statement? System.out.println ("1" + 3);
Q 102) What will be the default values of all the elements of an array defined as an instance variable?
Q 103) What is an Iterator

Q 104) what is the difference betwen action class and business class?

Q 105) what is domains and fields in project?can anyy one explain to me?
Q 106) plz can anybody give the description on banking domain knowledge.bcoz i have to work on banking project. im surfing most of the internet but i didn't get anything useful for me. everyone say about it indirectly but i didn't get them in a right way.plz help me
Q 107) Hai,I am working as a Technical Trainer on java/j2ee.I want increase knowledge on Telecome Domain.Please Help me

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