Garbage Collection Interview Questions
117) What is Garbage Collection?
Garbage collection is a process of reclaiming
the runtime unused objects.It is performed for memory management.
118) What is gc()?
gc() is a daemon thread.gc() method is defined in
System class that is used to send request to JVM to perform garbage collection.
119) What is the purpose of finalize() method?
finalize() method is invoked just before the
object is garbage collected.It is used to perform cleanup processing.
120) Can an unrefrenced objects be refrenced
again?
Yes.
121)What kind of thread is the Garbage
collector thread?
Daemon thread.
122)What is difference between final, finally
and finalize?
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final: final is a keyword, final can be variable, method or
class.You, can't change the value of final variable, can't override final
method, can't inherit final class.
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finally: finally block is used in exception
handling. finally block is always executed.
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finalize():finalize() method is used in garbage
collection.finalize() method is invoked just before the object is garbage
collected.The finalize() method can be used to perform any cleanup
processing.
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123)What is the purpose of the Runtime class?
The purpose of the Runtime class is to provide
access to the Java runtime system.
124)How will you invoke any external process
in Java?
By Runtime.getRuntime().exec(?) method.
I/O Interview Questions
125)What is the difference between the
Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?
The Reader/Writer class hierarchy is
character-oriented, and the InputStream/OutputStream class hierarchy is
byte-oriented.
126)What an I/O filter?
An I/O filter is an object that reads from one
stream and writes to another, usually altering the data in some way as it is
passed from one stream to another.
Serialization Interview Questions
127) What is serialization?
Serialization is a process of writing the state
of an object into a byte stream.It is mainly used to travel object's state on
the network.
128) What is Deserialization?
Deserialization is the process of reconstructing
the object from the serialized state.It is the reverse operation of
serialization.
129) What is transient keyword?
130)What is Externalizable?
Externalizable interface is used to write the
state of an object into a byte stream in compressed format.It is not a marker
interface.
131)What is the difference between
Serializalble and Externalizable interface?
Serializable is a marker interface but
Externalizable is not a marker interface.When you use Serializable interface,
your class is serialized automatically by default. But you can override
writeObject() and readObject() two methods to control more complex object
serailization process. When you use Externalizable interface, you have a
complete control over your class's serialization process.
Networking Interview Questions
132)How do I convert a numeric IP address like
192.18.97.39 into a hostname like java.sun.com?
By InetAddress.getByName("192.18.97.39").getHostName()
where 192.18.97.39 is the IP address.
Reflection Interview Questions
133) What is reflection?
Reflection is the process of examining or
modifying the runtime behaviour of a class at runtime.It is used in:
- IDE
(Integreted Development Environment) e.g. Eclipse, MyEclipse, NetBeans.
- Debugger
- Test
Tools etc.
134) Can you access the private method from
outside the class?
Yes, by changing the runtime behaviour of a
class if the class is not secured.
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