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Core Java Interview Questions and Answers

Ques 46. Does Java have "goto"?

Ans. No.

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Ques 47. What synchronization constructs does Java provide? How do they work?
Ans. The two common features that are used are:
1. Synchronized keyword - Used to synchronize a method or a block of code. When you synchronize a method, you are in effect synchronizing the code within the method using the monitor of the current object for the lock.
The following have the same effect.
synchronized void foo() {
void foo() {
synchronized(this) {
If you synchronize a static method, then you are synchronizing across all objects of the same class, i.e. the monitor you are using for the lock is one per class, not one per object.
2. wait/notify. wait() needs to be called from within a synchronized block. It will first release the lock acquired from the synchronization and then wait for a signal. In Posix C, this part is equivalent to the pthread_cond_wait method, which waits for an OS signal to continue. When somebody calls notify() on the object, this will signal the code which has been waiting, and the code will continue from that point. If there are several sections of code that are in the wait state, you can call notifyAll() which will notify all threads that are waiting on the monitor for the current object. Remember that both wait() and notify() have to be called from blocks of code that are synchronized on the monitor for the current object.
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Ques 48. Does Java have multiple inheritance?
Ans. Java does not support multiple inheritence directly but it does thru the concept of interfaces.
We can make a class implement a number of interfaces if we want to achieve multiple inheritence type of functionality of C++.
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Ques 49. How does exception handling work in Java?
Ans. 1.It separates the working/functional code from the error-handling code by way of try-catch clauses.
2.It allows a clean path for error propagation. If the called method encounters a situation it can't manage, it can throw an exception and let the calling method deal with it.
3.By enlisting the compiler to ensure that "exceptional" situations are anticipated and accounted for, it enforces powerful coding.
4.Exceptions are of two types: Compiler-enforced exceptions, or checked exceptions. Runtime exceptions, or unchecked exceptions. Compiler-enforced (checked) exceptions are instances of the Exception class or one of its subclasses '?? excluding the RuntimeException branch. The compiler expects all checked exceptions to be appropriately handled. Checked exceptions must be declared in the throws clause of the method throwing them '?? assuming, of course, they're not being caught within that same method. The calling method must take care of these exceptions by either catching or declaring them in its throws clause. Thus, making an exception checked forces the us to pay heed to the possibility of it being thrown. An example of a checked exception is java.io.IOException. As the name suggests, it throws whenever an input/output operation is abnormally terminated.
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Ques 50. Does Java have destructors?
Ans. Garbage collector does the job working in the background
Java does not have destructors; but it has finalizers that does a similar job.
the syntax is
public void finalize(){
if an object has a finalizer, the method is invoked before the system garbage collects the object
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