Java Questions

Q:

What are the types of Collision Resolution Techniques and the methods used in each of the type?

Answer

Open addressing (closed hashing),


The methods used include: Overflow block,


 Closed addressing (open hashing)


The methods used include: Linked list, Binary tree…

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Subject: Java - Technology

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Q:

try { int x = Integer.parseInt("two"); }

Which could be used to create an appropriate catch block?

A) ClassCastException B) IllegalStateException
C) NumberFormatException D) None
 
Answer & Explanation Answer: C) NumberFormatException

Explanation:

C is correct. 'Integer.parseInt' can throw a NumberFormatException, and IllegalArgumentException is its superclass 

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Q:

Should a main() method be compulsorily declared in all java classes?

Answer No not required. main() method should be defined only if the source class is a java application.
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Subject: Java - Technology

10 5888
Q:

void waitForSignal() {

Object obj = new Object();

synchronized (Thread.currentThread()) {

obj.wait();

obj.notify();

}

}

Which statement is true?

A) This code can throw an InterruptedException. B) This code can throw an IllegalMonitorStateException.
C) This code can throw a TimeoutException after ten minutes D) All the above
 
Answer & Explanation Answer: B) This code can throw an IllegalMonitorStateException.

Explanation:

It will throw  IllegalMonitorStateException.

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Job Role: IT Trainer

3 5882
Q:

Can you give few examples of final classes defined in Java API?

Answer

java.lang.String,  java.lang.Math are final classes.

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Subject: Java - Technology

5 5677
Q:

I want to print "Hello" even before main() is executed. How will you acheive that?

Answer Print the statement inside a static block of code. Static blocks get executed when the class gets loaded into the memory and even before the creation of an object. Hence it will be executed before the main() method. And it will be executed only once.
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Q:

How are this() and super() used with constructors?

Answer

Constructors use this to refer to another constructor in the same class with a different parameter list.


Constructors use super to invoke the superclass's constructor. If a constructor uses super, it must use it in the first line; otherwise, the compiler will complain.

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Q:

What are the restriction imposed on a static method or a static block of code?

Answer A static method should not refer to instance variables without creating an instance and cannot use "this" operator to refer the instance.
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