Two theoretical questions from javaprepare

[Sachin Kapoor]

I got these two wrong.

Which of the following statements are true. Select the two correct answers.

1. The wait method defined in the Thread class, can be used to convert a thread from Running state to Waiting state.
2. The wait(), notify(), and notifyAll() methods must be executed in synchronized code.
3. The notify() and notifyAll() methods can be used to signal and move waiting threads to ready-to-run state.
4. The Thread class is an abstract class.

I chose 1,2. The correct answer is 2,3. Why is 1 wrong? wait method causes thread to go from Running to Waiting state, doesn't it? Why is 3 right? notify method causes only 1 thread (not all waiting threads) to go from waiting to runnable, right?

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Which of these are core interfaces in the collection framework. Select the one correct answer.

1. Tree
2. Stack
3. Queue
4. Array
5. LinkedList
6. Map

I chose 3. The correct answer is 6. Queue extends from Collection, doesn't it? While Map does not. So why is 3 wrong and 6 right?

[Henry Wong]

1. The wait method defined in the Thread class, can be used to convert a thread from Running state to Waiting state.

The wait() method is defined in the Object class. This is probably the piece of knowledge the question was trying to test.

Henry

[Sachin Kapoor]

Thanks. That solves 1 problem.

Originally posted by Henry Wong:


The wait() method is defined in the Object class. This is probably the piece of knowledge the question was trying to test.

Henry

[Jesper de Jong]

About the second question: For which version of SCJP / Java was this test?

There is indeed an interface Queue, but it was added in Java 5. So if this test was for Java 1.4, then Queue would have been a wrong answer.

[Sachin Kapoor]

That solves it. Thanks!

Originally posted by Jesper Young:
About the second question: For which version of SCJP / Java was this test?

There is indeed an interface Queue, but it was added in Java 5. So if this test was for Java 1.4, then Queue would have been a wrong answer.