Quiz : Mock Questions for Preparation

1) Will this work?

public static void main(String args[])
{
RuntimeException re;
throw re;
}

Ans -> No , compile time exception :: variable re may not have been initialized

2) NumberFormatException is a subclass of IOException

3) if ("string".toUpperCase() =="STRING")
{
System.out.println("Yes");
}
else System.out.println("No");

Ans -> No // if we use .equals() here , then we get “yes” . This is because , “string” and “STRING” are two separate object references pointing to two separate objects. == is used to compare whether two object references point to same object or not. .equals() compares the objects for their contents.

3) when we extend a class , the static class variables are also passed on to the child class. Final class variables are not passed. TrAnsient class variables are passes( they are implicitly initialized ).

4) We cannot extend a math class ( its final) . all its constants and methods are static.

5) We cannot instantiate a math class .. its constructors are private.

5) class XTC {

public static void main ( String [ ] ka ) {
int s = 64 / 9 ;
float f = 64 / 9 ;
double d = 64 / 9 ;
System . out . println ( s + " & " + f + " & " + d ) ;
}
};

Ans -> 7 , 7.0 , 7.0

6) What is the output of the following ? Will it compile at all ?

class XTC {

public static void main ( String [ ] ka ) {
Integer b = new Integer(3) ;
System . out . println ( b instanceof Integer ) ;

}
};

Ans -> true

7) What is the output of the following ? Will it compile at all ?

class XTC {

public static void main ( String [ ] ka ) {
Integer b = null;
System . out . println ( b instanceof Integer ) ;

}
};

Ans -> false

8) What is the output of the following ? Will it compile at all ?

class XTC {

public static void main ( String [ ] ka ) {
Integer b = null;
System . out . println ( b instanceof Object ) ;

}
};

Ans -> false

9) What is the output of the following ? Will it compile at all ?

class XTC {

public static void main ( String [ ] ka ) {
Integer b = new Integer(3);
System . out . println ( b instanceof Object ) ;

}
};

Ans -> true

10) if (Double . POSITIVE_INFINITY == Double . POSITIVE_INFINITY )
{
System . out . println ( “Yes”) ;
}

Ans -> Yes