Java Interview question 5

Q: When a thread is created and started, what is its initial state?
A: A thread is in the ready state after it has been created and started.


Q: What is the purpose of finalization?
A: The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.


Q: What is the Locale class?
A: The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.

Q: What is the difference between a while statement and a do statement?
A: A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once.


Q: What is the difference between static and non-static variables?
A: A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.


Q: How are this() and super() used with constructors?
A: This() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor.

Q: What are synchronized methods and synchronized statements?
A: Synchronized methods are methods that are used to control access to 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.

Q: What is daemon thread and which method is used to create the daemon thread?
A: Daemon thread is a low priority thread which runs intermittently in the back ground doing the garbage collection operation for the java runtime system. setDaemon method is used to create a daemon thread.

Question: When is the finally clause of a try-catch-finally statement executed?

Answer: The finally clause of the try-catch-finally statement is always executed unless the thread of execution terminates or an exception occurs within the execution of the finally clause.

Question: Which class is the immediate superclass of the Container class?

Answer: Component

Question: If a method is declared as protected, where may the method be accessed?

Answer: A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.

Question: How can the Checkbox class be used to create a radio button?

Answer: By associating Checkbox objects with a CheckboxGroup.

Q: Can applets communicate with each other?
A: At this point in time applets may communicate with other applets running in the same virtual machine. If the applets are of the same class, they can communicate via shared static variables. If the applets are of different classes, then each will need a reference to the same class with static variables. In any case the basic idea is to pass the information back and forth through a static variable.

An applet can also get references to all other applets on the same page using the getApplets() method of java.applet.AppletContext. Once you get the reference to an applet, you can communicate with it by using its public members.

It is conceivable to have applets in different virtual machines that talk to a server somewhere on the Internet and store any data that needs to be serialized there. Then, when another applet needs this data, it could connect to this same server. Implementing this is non-trivial.

Q: What are the steps in the JDBC connection?
A: While making a JDBC connection we go through the following steps :

Step 1 : Register the database driver by using :

Class.forName(\" driver classs for that specific database\" );

Step 2 : Now create a database connection using :

Connection con = DriverManager.getConnection(url,username,password);

Step 3: Now Create a query using :

Statement stmt = Connection.Statement(\"select * from TABLE NAME\");

Step 4 : Exceute the query :

stmt.exceuteUpdate();

Question: What is the difference between static and non-static variables?

Answer: A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.

Question: What is the difference between the paint() and repaint() methods?

Answer: The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.

Q: How does a try statement determine which catch clause should be used to handle an exception?
A:

When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exceptionis executed. The remaining catch clauses are ignored.