Java UPDATED ACTUAL Exam Questions
and CORRECT Answers
If you overwrite clone(), which 3 rules must this method obey? - CORRECT ANSWER -
1) the new object should be new: memory address should differ
2) Both should be an object of the same class
3) Both should be in the same state:
a.clone().equals(a) == true
Why do we need to implement the Clonable interface? - CORRECT ANSWER - At
runtime it would throw the CloneNotSupportedException if we don't implement the Cloneable
interface. A class implements the Cloneable interface to indicate to the Object.clone() method
that it is legal for that method to make a field-for-field copy of instances of that class.
What is a marker interface? - CORRECT ANSWER - A Marker interface, has no method.
Serializable, Clonable are marker interfaces.
How do you clone an object? - CORRECT ANSWER - MyClone a = (MyClone) c.clone()
- TypeCast is nessesary.
- handle CloneNotSupportedException
Why can Annotations replace marker interfaces? - CORRECT ANSWER - Annotations
can convey metadata about the class to its consumers without creating a separate type for it.
Annotations let you pass information to classes that "consume" it.
What is Double-Checked Locking? - CORRECT ANSWER - To reduce the overhead of
acquiring a lock by first testing the locking criterion without actually acquiring the lock.
How do you make an object serializable? - CORRECT ANSWER - The class must
implement the java.io.Serializable interface
,Java object serialization is performed using which classes? - CORRECT ANSWER - Java
object serialization (writing) is done with the ObjectOutputStream and deserialization (reading)
is done with the ObjectInputStream.
What is serialVersionUID? - CORRECT ANSWER - In addition to implementing the
Serializable interface, a class intended for serialization should also contain a private static final
long variable named serialVersionUID.
The serialVersionUID variable is used by Java's object serialization API to determine if a
deserialized object was serialized (written) with the same version of the class, as it is now
attempting to deserialize it into.
If you make changes to the class that affect serialization, you should also change its
serialVersionUID value.
What is escape analysis? - CORRECT ANSWER - escape analysis is a method for
determining the dynamic scope of pointers - where in the program a pointer can be accessed.
What is the size of byte? - CORRECT ANSWER - 8 bits
What is the size of char? - CORRECT ANSWER - 16 bits
What is the size of short? - CORRECT ANSWER - 16 bits
What is the size of int? - CORRECT ANSWER - 32 bits
what is the size of long? - CORRECT ANSWER - 64 bits
what is the size of float? - CORRECT ANSWER - 32 bits
what is the size of double? - CORRECT ANSWER - 64 bits
,What is the range of byte - CORRECT ANSWER - -128 to 127
What is the range of short? - CORRECT ANSWER - -32,768 to 32,767
What is the range of int? - CORRECT ANSWER - -2,1 billion to 2,1billion
How do you check if a number is even? - CORRECT ANSWER - check if number AND 1
is 0
How do you test if the n-th bit is set? - CORRECT ANSWER - Shift n times to the right
and then AND
How can you set the n-th bit - CORRECT ANSWER - Shift n times to the left and OR
How can you unset the nth bit - CORRECT ANSWER - Shift n times to the left and invert,
then AND
How can you toggle the nth Bit? - CORRECT ANSWER - Shift n times to the left and
XOR
How can you turn off the rightmost 1Bit? - CORRECT ANSWER - AND with (number -
1)
How can you return only 1 or 0 for the rightmost 1Bit value? - CORRECT ANSWER -
number & ( - number)
How can you also declare -x bitwise? - CORRECT ANSWER - ~x + 1
, What is ~0 bitwise? - CORRECT ANSWER -0
How can you right propagate the rightmost 1-bit? - CORRECT ANSWER - number OR
(number - 1), does not work for 0
What is -1 in twos complement? - CORRECT ANSWER - 1111 1111
How can you isolate the rightmost 0-bit? - CORRECT ANSWER - invert number AND
(number + 1)
How can you turn on the rightmost 0-bit. - CORRECT ANSWER - number OR (number +
1)
what algorithm is Arrays.sort? - CORRECT ANSWER - An improved quicksort with
average nlog(n) runtime
how can you sort a range of an array in-place? - CORRECT ANSWER - Arrays.sort(int[]
a, int fromIndex, int toIndex)
works with all primitive types and comparables
How can you sort an array using parallel tasks - CORRECT ANSWER -
Arrays.parallelSort usesmergesort and ForkJoin common pool to execute any parallel tasks.
works with all primitive types and comparables
How is the comparable interface implemented? - CORRECT ANSWER - public interface
Comparable<T>{
int compareTo(T o) {
return 1; //if this > that
return 0; //if this == that
return -1; //if this < that
and CORRECT Answers
If you overwrite clone(), which 3 rules must this method obey? - CORRECT ANSWER -
1) the new object should be new: memory address should differ
2) Both should be an object of the same class
3) Both should be in the same state:
a.clone().equals(a) == true
Why do we need to implement the Clonable interface? - CORRECT ANSWER - At
runtime it would throw the CloneNotSupportedException if we don't implement the Cloneable
interface. A class implements the Cloneable interface to indicate to the Object.clone() method
that it is legal for that method to make a field-for-field copy of instances of that class.
What is a marker interface? - CORRECT ANSWER - A Marker interface, has no method.
Serializable, Clonable are marker interfaces.
How do you clone an object? - CORRECT ANSWER - MyClone a = (MyClone) c.clone()
- TypeCast is nessesary.
- handle CloneNotSupportedException
Why can Annotations replace marker interfaces? - CORRECT ANSWER - Annotations
can convey metadata about the class to its consumers without creating a separate type for it.
Annotations let you pass information to classes that "consume" it.
What is Double-Checked Locking? - CORRECT ANSWER - To reduce the overhead of
acquiring a lock by first testing the locking criterion without actually acquiring the lock.
How do you make an object serializable? - CORRECT ANSWER - The class must
implement the java.io.Serializable interface
,Java object serialization is performed using which classes? - CORRECT ANSWER - Java
object serialization (writing) is done with the ObjectOutputStream and deserialization (reading)
is done with the ObjectInputStream.
What is serialVersionUID? - CORRECT ANSWER - In addition to implementing the
Serializable interface, a class intended for serialization should also contain a private static final
long variable named serialVersionUID.
The serialVersionUID variable is used by Java's object serialization API to determine if a
deserialized object was serialized (written) with the same version of the class, as it is now
attempting to deserialize it into.
If you make changes to the class that affect serialization, you should also change its
serialVersionUID value.
What is escape analysis? - CORRECT ANSWER - escape analysis is a method for
determining the dynamic scope of pointers - where in the program a pointer can be accessed.
What is the size of byte? - CORRECT ANSWER - 8 bits
What is the size of char? - CORRECT ANSWER - 16 bits
What is the size of short? - CORRECT ANSWER - 16 bits
What is the size of int? - CORRECT ANSWER - 32 bits
what is the size of long? - CORRECT ANSWER - 64 bits
what is the size of float? - CORRECT ANSWER - 32 bits
what is the size of double? - CORRECT ANSWER - 64 bits
,What is the range of byte - CORRECT ANSWER - -128 to 127
What is the range of short? - CORRECT ANSWER - -32,768 to 32,767
What is the range of int? - CORRECT ANSWER - -2,1 billion to 2,1billion
How do you check if a number is even? - CORRECT ANSWER - check if number AND 1
is 0
How do you test if the n-th bit is set? - CORRECT ANSWER - Shift n times to the right
and then AND
How can you set the n-th bit - CORRECT ANSWER - Shift n times to the left and OR
How can you unset the nth bit - CORRECT ANSWER - Shift n times to the left and invert,
then AND
How can you toggle the nth Bit? - CORRECT ANSWER - Shift n times to the left and
XOR
How can you turn off the rightmost 1Bit? - CORRECT ANSWER - AND with (number -
1)
How can you return only 1 or 0 for the rightmost 1Bit value? - CORRECT ANSWER -
number & ( - number)
How can you also declare -x bitwise? - CORRECT ANSWER - ~x + 1
, What is ~0 bitwise? - CORRECT ANSWER -0
How can you right propagate the rightmost 1-bit? - CORRECT ANSWER - number OR
(number - 1), does not work for 0
What is -1 in twos complement? - CORRECT ANSWER - 1111 1111
How can you isolate the rightmost 0-bit? - CORRECT ANSWER - invert number AND
(number + 1)
How can you turn on the rightmost 0-bit. - CORRECT ANSWER - number OR (number +
1)
what algorithm is Arrays.sort? - CORRECT ANSWER - An improved quicksort with
average nlog(n) runtime
how can you sort a range of an array in-place? - CORRECT ANSWER - Arrays.sort(int[]
a, int fromIndex, int toIndex)
works with all primitive types and comparables
How can you sort an array using parallel tasks - CORRECT ANSWER -
Arrays.parallelSort usesmergesort and ForkJoin common pool to execute any parallel tasks.
works with all primitive types and comparables
How is the comparable interface implemented? - CORRECT ANSWER - public interface
Comparable<T>{
int compareTo(T o) {
return 1; //if this > that
return 0; //if this == that
return -1; //if this < that
