Mock Questions for Test 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
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2) NumberFormatException is a subclass of IOException

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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.
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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 ).

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

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

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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

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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

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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

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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

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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

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

Ans -> Yes

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