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Java interview questions-7 (Exception Handling and Multi Threading)
Posted Date: 19 Dec 2007 Resource Type: Articles/Knowledge Sharing Category: Study Abroad
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Posted By: BHARATH Member Level: Gold
Rating:  Points: 5
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Exception Handling
1) What is the difference between ‘throw’ and ‘throws’ ?And it’s application?
Ans : Exceptions that are thrown by java runtime systems can be handled by Try and catch blocks. With throw exception we can handle the exceptions thrown by the program itself. If a method is capable of causing an exception that it does not
handle, it must specify this behavior so the callers of the method can guard
against that exception.
2) What is the difference between ‘Exception’ and ‘error’ in java?
Ans : Exception and Error are the subclasses of the Throwable class. Exception class is used for exceptional conditions that user program should catch. With exception class we can subclass to create our own custom exception.
Error defines exceptions that are not excepted to be caught by you program. Example is Stack Overflow.
3) What is ‘Resource leak’?
Ans : Freeing up other resources that might have been allocated at the beginning of a method.
4)What is the ‘finally’ block?
Ans : Finally block will execute whether or not an exception is thrown. If an exception is thrown, the finally block will execute even if no catch statement match the exception. Any time a method is about to return to the caller from inside try/catch block, via an uncaught exception or an explicit return statement, the finally clause is also execute.
5) Can we have catch block with out try block? If so when?
Ans : No. Try/Catch or Try/finally form a unit.
6) What is the difference between the following statements?
Catch (Exception e),
Catch (Error err),
Catch (Throwable t)
Ans :
7) What will happen to the Exception object after exception handling?
Ans : It will go for Garbage Collector. And frees the memory.
8) How many Exceptions we can define in ‘throws’ clause?
Ans : We can define multiple exceptions in throws clause.
Signature is..
type method-name (parameter-list) throws exception-list
9) The finally block is executed when an exception is thrown, even if no catch matches it.
True/False
Ans : True
10) The subclass exception should precede the base class exception when used within the catch clause.
True/False
Ans : True
11) Exceptions can be caught or rethrown to a calling method.
True/False
Ans : True
12) The statements following the throw keyword in a program are not executed.
True/False
Ans : True
13) The toString ( ) method in the user-defined exception class is overridden.
True/False
Ans : True
MULTI THREADING:-
1) What are the two types of multitasking?
Ans : 1.process-based
2.Thread-based
2) What are the two ways to create the thread?
Ans : 1.by implementing Runnable
2.by extending Thread
3) What is the signature of the constructor of a thread class?
Ans : Thread(Runnable threadob,String threadName)
4) What are all the methods available in the Runnable Interface?
Ans : run()
5) What is the data type for the method isAlive() and this method is
available in which class?
Ans : boolean, Thread
6) What are all the methods available in the Thread class?
Ans : 1.isAlive()
2.join()
3.resume()
4.suspend()
5.stop()
6.start()
7.sleep()
8.destroy()
7) What are all the methods used for Inter Thread communication and what is the class in which these methods are defined?
Ans :1. wait(),notify() & notifyall()
2. Object class
8) What is the mechanisam defind by java for the Resources to be used by only one Thread at a time?
Ans : Synchronisation
9) What is the procedure to own the moniter by many threads?
Ans : not possible
10) What is the unit for 1000 in the below statement?
ob.sleep(1000)
Ans : long milliseconds
11) What is the data type for the parameter of the sleep() method?
Ans : long
12) What are all the values for the following level?
max-priority
min-priority
normal-priority
Ans : 10,1,5
13) What is the method available for setting the priority?
Ans : setPriority()
14) What is the default thread at the time of starting the program?
Ans : main thread
15) The word synchronized can be used with only a method.
True/ False
Ans : False
16) Which priority Thread can prompt the lower primary Thread?
Ans : Higher Priority
17) How many threads at a time can access a monitor?
Ans : one
18) What are all the four states associated in the thread?
Ans : 1. new 2. runnable 3. blocked 4. dead
19) The suspend()method is used to teriminate a thread?
True /False
Ans : False
20) The run() method should necessary exists in clases created as subclass of thread?
True /False
Ans : True
21) When two threads are waiting on each other and can't proceed the programe is said to be in a deadlock?
True/False
Ans : True
22) Which method waits for the thread to die ?
Ans : join() method
23) Which of the following is true?
1) wait(),notify(),notifyall() are defined as final & can be called only from with in a synchronized method
2) Among wait(),notify(),notifyall() the wait() method only throws IOException
3) wait(),notify(),notifyall() & sleep() are methods of object class
1
2
3
1 & 2
1,2 & 3
Ans : D
24) Garbage collector thread belongs to which priority?
Ans : low-priority
25) What is meant by timeslicing or time sharing?
Ans : Timeslicing is the method of allocating CPU time to individual threads in a priority schedule.
26) What is meant by daemon thread? In java runtime, what is it's role?
Ans : Daemon thread is a low priority thread which runs intermittently in the background doing the garbage collection operation for the java runtime system.
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