Sample Questions Best site for GRE, LSAT, SAT, GMAT, TOEFL, CCNA, CCSA and interview sample questions  

Technical Sample Questions : C |  C++ |  Oracle |  Java | Unix |  Operating Systems |  Data Structure

Java Sample Questions ›› Java questions

Technical General Java Sample Questions

  1. How can my application get to know when a HttpSession is removed?

    Answer: Define a Class HttpSessionNotifier which implements HttpSessionBindingListener and implement the functionality what you need in valueUnbound() method. Create an instance of that class and put that instance in HttpSession.

  2. Whats the difference between notify() and notifyAll()?

    Answer: notify() is used to unblock one waiting thread; notifyAll() is used to unblock all of them. Using notify() is preferable (for efficiency) when only one blocked thread can benefit from the change (for example, when freeing a buffer back into a pool). notifyAll() is necessary (for correctness) if multiple threads should resume.

  3. Why can't I say just abs() or sin() instead of Math.abs() and Math.sin()?

    Answer: The import statement does not bring methods into your local name space. It lets you abbreviate class names, but not get rid of them altogether. That's just the way it works, you'll get used to it. It's really a lot safer this way. However, there is actually a little trick you can use in some cases that gets you what you want. If your top-level class doesn't need to inherit from anything else, make it inherit from java.lang.Math. That *does* bring all the methods into your local name space. But you can't use this trick in an applet, because you have to inherit from java.awt.Applet. And actually, you can't use it on java.lang.Math at all, because Math is a "final" class which means it can't be extended.

  4. Why are there no global variables in Java?

    Answer: Global variables are considered bad form for a variety of reasons: Adding state variables breaks referential transparency (you no longer can understand a statement or expression on its own: you need to understand it in the context of the settings of the global variables), State variables lessen the cohesion of a program: you need to know more to understand how something works. A major point of Object-Oriented programming is to break up global state into more easily understood collections of local state, When you add one variable, you limit the use of your program to one instance. What you thought was global, someone else might think of as local: they may want to run two copies of your program at once. For these reasons, Java decided to ban global variables.

  5. What does it mean that a class or member is final?

    Answer: A final class can no longer be subclassed. Mostly this is done for security reasons with basic classes like String and Integer. It also allows the compiler to make some optimizations, and makes thread safety a little easier to achieve. Methods may be declared final as well. This means they may not be overridden in a subclass. Fields can be declared final, too. However, this has a completely different meaning. A final field cannot be changed after it's initialized, and it must include an initializer statement where it's declared. For example, public final double c = 2.998; It's also possible to make a static field final to get the effect of C++'s const statement or some uses of C's #define, e.g. public static final double c = 2.998;

  6. What does it mean that a method or class is abstract?

    Answer: An abstract class cannot be instantiated. Only its subclasses can be instantiated. You indicate that a class is abstract with the abstract keyword like this: public abstract class Container extends Component {Abstract classes may contain abstract methods. A method declared abstract is not actually implemented in the current class. It exists only to be overridden in subclasses. It has no body. For example, public abstract float price();Abstract methods may only be included in abstract classes. However, an abstract class is not required to have any abstract methods, though most of them do. Each subclass of an abstract class must override the abstract methods of its superclasses or itself be declared abstract.

  7. What is a transient variable?

    Answer: transient variable is a variable that may not be serialized.

  8. How are Observer and Observable used?

    Answer: Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.

  9. Can a lock be acquired on a class?

    Answer: Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.

  10. What state does a thread enter when it terminates its processing?

    Answer: When a thread terminates its processing, it enters the dead state.

« Previous || Next »

Java Sample Question Number: 1-10| 11-20| 21-30| 31-40| 41-50| 51-60| 61-70| 71-80| 81-90| 91-100| 101-110| 111-120| 121-130| 131-140| 141-150| 151-160| 161-170| 171-180| 181-190| 191-200| 201-210| 211-220| 221-230| 231-240| 241-250| 251-260| 261-270| 271-280| 281-290| 291-300| 301-310| 311-320| 321-330
Sample Test Questions
GRE Sample Questions
CAT Sample Questions
GMAT Sample Questions
TOEFL Sample Questions
ACT Sample Questions
SAT Sample Questions
LSAT Sample Questions
PSAT Sample Questions
MCAT Sample Questions
PMP Sample Questions
GED Sample Questions
ECDL Sample Questions
DMV Sample Questions
CCNA Sample Questions
MCSE Sample Questions
Network+ Sample Questions
A+ Sample Questions
Technical Sample Questions
WASL Sample Questions
CISA Sample Questions

Other Sample Questions
Sample Interview Questions
Sample Teacher Interview Questions
Sample Citizenship Questions
Accuplacer Sample Questions
Science Bowl sample Questions
Driving Test Sample Questions
Sample Survey Questions Sample Essay Questions
Sample Behavioral Interview Questions

Copyright © 2004-2013, Best BSQ. All Rights Reserved.