This week's book giveaway is in the Servlets forum.
We're giving away four copies of Murach's Java Servlets and JSP and have Joel Murach on-line!
See this thread for details.
The moose likes Programmer Certification (SCJP/OCPJP) and the fly likes doubts in mock exam ques Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login


Win a copy of Murach's Java Servlets and JSP this week in the Servlets forum!
JavaRanch » Java Forums » Certification » Programmer Certification (SCJP/OCPJP)
Bookmark "doubts in mock exam ques" Watch "doubts in mock exam ques" New topic
Author

doubts in mock exam ques

Mamta Jha
Greenhorn

Joined: Oct 18, 2000
Posts: 8
hi friends,
These are some of the quest from a mock exam-
Q1. Which of the following are true about the class defined inside an interface
1> it is not possible in the java Laungage. //ans
2> The class is always public.
3> The class is always static.
4> the class methods cannot call the methods declared in the interface.
5> the class methods can call only the static methods declared in the interface.
my ans is 2.
Q2.What does the following expression return
Math.max(Float.POSITIVE_INFINITY,Double.POSITIVE_INFINITY);
1>Float.POSITIVE_INFINITY
2>Double.POSITIVE_INFINITY //ans
3>runtime Exception
when I tried this using a code , the answer comes id infinity.Does Double.POSITIVE_INFINITY and infinity mean the same.
Q3.Assume that th is an instance holding a thread object. th.start() causes the thread to start running and eventually complete its execution. The object reference by th is not accessable any more and is garbage collected when the garbage collecter runs.
True
False //ans
Shouldn't the thread object get gced after completion of run? so the ans should be true.
Q4. can we explicitly call the constructor of an abstract class?
I'll be thankful if anyone could give the correct explanation for these.
Mamta
Jane Griscti
Ranch Hand

Joined: Aug 30, 2000
Posts: 3141
Hi Mamta,
Q1. 1 - TRUE. An Interface can contain constants and empty method declarations but NOT classes. Classes and Interfaces are both types in Java. (see JLS�.4.3)
Correction: Sorry Mamta. Just discovered that you CAN declare classes within an interface. Any classes nested inside an interface are Static and Public.

Q2. The value does print as just Infinity. When I ran a test using the following code both if statements printed.

So I don't think, for practical purposes, the two values are different. The JSK defines them as


Q3. Think the answer is FALSE. The Java Programming Language states "when a thread dies, its object doesn't go away" which I interpret to mean just because a thread ends does not mean the object is available for gc.
Q4. Think the answer to this is Yes. An abstract class cannot be instantiated BUT a subclass of an abstract can use super() to call an abstract class ctor.

Hope that helps.
------------------
Jane
[This message has been edited by Jane Griscti (edited October 21, 2000).]
[This message has been edited by Jane Griscti (edited October 21, 2000).]
[This message has been edited by Jane Griscti (edited October 21, 2000).]


Jane Griscti
SCJP, Co-author Mike Meyers' Java 2 Certification Passport
suneeta prattipati
Greenhorn

Joined: Oct 16, 2000
Posts: 8
Hi Mamta,
ans to Q3)
the start() method does not cause the thread to start running. You need the run method for that. start() just makes the thread eligible to run. So the ans is FALSE.
Mamta Jha
Greenhorn

Joined: Oct 18, 2000
Posts: 8
thanks jane & suneeta
mamta
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: doubts in mock exam ques
 
Similar Threads
Doubt on Class defined inside an interface
doubt : class defined inside an interface
Mock Question (Help)
What does the following expression return ?
Question on Interface