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:

class Hell {

public static void main(String[] args) {

Integer i = 42;

String s = (i<40)?"life":(i>50)?"base":"ball";

System.out.println(s);

}

}

A) null B) ball
C) base D) None
 
Answer & Explanation Answer: B) ball

Explanation:

D is correct. This is a ternary nested in a ternary with a little unboxing thrown in.Both of the ternary expressions are false.

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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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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 6337
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

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Q:

public abstract class Shape {

private int x;

private int y;

public abstract void draw();

public void setAnchor(int x, int y) {

this.x = x;

this.y = y;

}

}

Which two classes use the Shape class correctly?

A) public class Circle implements Shape { private int radius; B) public abstract class Circle extends Shape { private int radius; }
C) public class Circle extends Shape { private int radius; public void draw(); D) None
 
Answer & Explanation Answer: B) public abstract class Circle extends Shape { private int radius; }

Explanation:

Only B is true

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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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