ABSOLUTE JAVA COMPREHENSIVE EXAM
SCRIPT VERIFIED QUESTIONS AND
SOLUTIONS GRADED APLUS
●● Why do we need to implement the Clonable interface?
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?
Answer: A Marker interface, has no method.
Serializable, Clonable are marker interfaces.
●● How do you clone an object?
Answer: MyClone a = (MyClone) c.clone()
- TypeCast is nessesary.
- handle CloneNotSupportedException
●● Why can Annotations replace marker interfaces?
,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?
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?
Answer: The class must implement the java.io.Serializable interface
●● Java object serialization is performed using which classes?
Answer: Java object serialization (writing) is done with the
ObjectOutputStream and deserialization (reading) is done with the
ObjectInputStream.
●● What is serialVersionUID?
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?
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?
Answer: 8 bits
●● What is the size of char?
Answer: 16 bits
●● What is the size of short?
Answer: 16 bits
●● What is the size of int?
Answer: 32 bits
●● what is the size of long?
Answer: 64 bits
●● what is the size of float?
Answer: 32 bits
, ●● what is the size of double?
Answer: 64 bits
●● What is the range of byte
Answer: -128 to 127
●● What is the range of short?
Answer: -32,768 to 32,767
●● What is the range of int?
Answer: -2,1 billion to 2,1billion
●● How do you check if a number is even?
Answer: check if number AND 1 is 0
●● How do you test if the n-th bit is set?
Answer: Shift n times to the right and then AND
●● How can you set the n-th bit
Answer: Shift n times to the left and OR
SCRIPT VERIFIED QUESTIONS AND
SOLUTIONS GRADED APLUS
●● Why do we need to implement the Clonable interface?
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?
Answer: A Marker interface, has no method.
Serializable, Clonable are marker interfaces.
●● How do you clone an object?
Answer: MyClone a = (MyClone) c.clone()
- TypeCast is nessesary.
- handle CloneNotSupportedException
●● Why can Annotations replace marker interfaces?
,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?
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?
Answer: The class must implement the java.io.Serializable interface
●● Java object serialization is performed using which classes?
Answer: Java object serialization (writing) is done with the
ObjectOutputStream and deserialization (reading) is done with the
ObjectInputStream.
●● What is serialVersionUID?
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?
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?
Answer: 8 bits
●● What is the size of char?
Answer: 16 bits
●● What is the size of short?
Answer: 16 bits
●● What is the size of int?
Answer: 32 bits
●● what is the size of long?
Answer: 64 bits
●● what is the size of float?
Answer: 32 bits
, ●● what is the size of double?
Answer: 64 bits
●● What is the range of byte
Answer: -128 to 127
●● What is the range of short?
Answer: -32,768 to 32,767
●● What is the range of int?
Answer: -2,1 billion to 2,1billion
●● How do you check if a number is even?
Answer: check if number AND 1 is 0
●● How do you test if the n-th bit is set?
Answer: Shift n times to the right and then AND
●● How can you set the n-th bit
Answer: Shift n times to the left and OR
