Java Interview Questions with Answers (Part 2)

on 4:35 AM

The second episode of Java Interview Questions with Answers here
  • Which containers use a border layout as their default layout?
  • How are Observer and Observable used?
  • What is synchronization and why is it important?
  • What are synchronized methods and synchronized statements?
  • What are three ways in which a thread can enter the waiting state?
  • Can a lock be acquired on a class?
  • What's new with the stop(), suspend() and resume() methods in JDK 1.2?
  • What is the preferred size of a component?
  • What's the difference between J2SDK 1.5 and J2SDK 5.0?
  • What would you use to compare two String variables - the operator == or the method equals()?
  • What is thread?
  • What is multi-threading?
  • How does multi-threading take place on a computer with a single CPU?
  • How to create a thread in a program?
  • Can Java object be locked down for exclusive use by a given thread?
Which containers use a border Layout as their default layout?
The window, Frame and Dialog classes use a border layout as their default layout.
How are Observer and Observable used?
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.
What is synchronization and why is it important?
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often causes dirty data and leads to significant errors.
What are synchronized methods and synchronized statements?
Synchronized methods are methods that are used to control access to a method or an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
 What are three ways in which a thread can enter the waiting state?
A thread can enter the waiting state by invoking its sleep() method, by blocking on IO, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.
Can a lock be acquired on a class?
Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.
What's new with the stop(), suspend() and resume() methods in JDK 1.2?
The stop(), suspend() and resume() methods have been deprecated in JDK 1.2.
What is the preferred size of a component?
The preferred size of a component is the minimum component size that will allow the component to display normally.
What's the difference between J2SDK 1.5 and J2SDK 5.0?
There's no difference, Sun Microsystems just re-branded this version.

What would you use to compare two String variables - the operator == or the method equals()?
I'd use the method equals() to compare the values of the Strings and the == to check if two variables point at the same instance of a String object.
What is thread?
A thread is an independent path of execution in a system.
 What is multi-threading?
Multi-threading means various threads that run in a system.

How does multi-threading take place on a computer with a single CPU?
The operating system's task scheduler allocates execution time to multiple tasks. By quickly switching between executing tasks, it creates the impression that tasks execute sequentially.
How to create a thread in a program?
You have two ways to do so. First, making your class "extends" Thread class. Second, making your class "implements" Runnable interface. Put jobs in a run() method and call start() method to start the thread.
Can Java object be locked down for exclusive use by a given thread?

Yes. You can lock an object by putting it in a "synchronized" block. The locked object is inaccessible to any thread other than the one that explicitly claimed it.









2 comments:

mary Brown said...
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mary Brown said...

Great Article
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