Tag: programming languages

Questions Related to programming languages

If you call the interrupted() method of a thread object twice the second call will always return false.
technology programming languages

  1. True

  2. False

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Correct Option: B

A number of threads of the same priority have relinquished the lock on a monitor and are in a waiting state after having called the wait() method of the object. A new thread enters the monitor and calls the notifyAll() method of the meonitor. Which of these threads will be the first one to resume?
technology programming languages

  1. The thread that has been waiting the longest.

  2. The thread that was the last one to to exit the monitor.

  3. You can never be sure which thread will get to run first.

  4. The the first thread that called the wait() method

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Correct Option: C

Which of these are valid contructors of a Thread object.
technology programming languages

  1. public Thread(Object obj)

  2. public Thread(String name)

  3. public Thread(Runnable trgt)

  4. public Thread(ThreadGroup grp, Runnable trgt, String name)

  5. public Thread(ThreadGroup grp, Object ob)

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Correct Option: B,C,D

class Line { Line 1. public class Point { public int x,y; } Line 2. public Point getPoint() { return new Point(); } Line 3. } Line 4. class Triangle { Line 5. public Triangle() { Line 6. // insert code here Line 7. } 18. } Which code, inserted at line Line 6, correctly retrieves a local instance of a Point object? A. Point p = Line.getPoint(); B. Line.Point p = Line.getPoint(); C. Point p = (new Line()).getPoint(); D. Line.Point p = (new Line()).getPoint();
technology programming languages

  1. A

  2. B

  3. C

  4. D

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Correct Option: D

public class test { Line 1. public static void main(String [] a) { Line 2. assert a.length == 1; Line 3. } Line 4. } Which two will produce an AssertionError? (Choose two.) A. java test B. java -ea test C. java test file1 D. java -ea test file1 E. java -ea test file1 file2 F. java -ea:test test file1
technology programming languages

  1. AB

  2. BC

  3. AE

  4. BE

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Correct Option: D

Given a method that must ensue that its parameter is not null: Line 1. public void someMethod(Object value) { Line 2. // check for null value Line 3. System.out.println(value.getClass()); Line 4. } What, inserted at line 2, is the appropriate way to handle a null value? A. assert value == null; B. assert value !null, “value is null”; C. if (value == null) { throw new AssertionException(”value is null”); D. if (value == null) { throw new IllegalArgumentException(”value is null”);
technology programming languages

  1. A

  2. B

  3. C

  4. D

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Correct Option: D

Line 1. public class ClassA { Line 2. public void count(int i) { Line 3. count(++i); Line 4. } Line 5. } And: Line 6. ClassA a = new ClassA(); Line 7. a.count(3); Which exception or error should be thrown by the virtual machine? A. StackOverflowError B. NullPointerException C. NumberFormatException D. IllegalArgumentException E. ExceptionlnlnitializerError
technology programming languages

  1. A

  2. B

  3. C

  4. D

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Correct Option: D

public class Foo implements java.io.Serializable { Line1. private int x; Line2. public int getX() { return x; } Line 3.publicFoo(int x){this.x=x; } Line 4. private void writeObject( ObjectOutputStream s) Line 5. throws IOException { Line 6. // insert code here Line 7. } Line 8. } Which code fragment, inserted at line Line 6, will allow Foo objects to be correctly serialized and deserialized? A. s.writeInt(x); B. s.serialize(x); C. s.writeObject(x); D. s.defaultWriteObject();

technology programming languages

  1. A

  2. B

  3. C

  4. D

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Correct Option: D

Which declare a compilable abstract class? (Choose all that apply.)

technology programming languages

  1. public abstract class Canine { public Bark speak(); }

  2. public abstract class Canine { public Bark speak() { } }

  3. public class Canine { public abstract Bark speak(); }

  4. public class Canine abstract { public abstract Bark speak(); }

Show answer
Correct Option: B

AI Explanation

To answer this question, we need to understand the concept of abstract classes and how they are declared in Java.

An abstract class is a class that cannot be instantiated and is meant to be extended by other classes. It may contain abstract methods, which are methods without any implementation, as well as regular methods with implementations.

Let's go through each option to understand why it is correct or incorrect:

Option A) public abstract class Canine { public Bark speak(); } This option is incorrect because the abstract method "speak()" is not given an implementation. Abstract methods must be implemented in the concrete subclass that extends the abstract class.

Option B) public abstract class Canine { public Bark speak() { } } This option is correct because it declares an abstract class "Canine" with a concrete method "speak()" that returns a "Bark" object. The method implementation can be empty, as long as it is provided.

Option C) public class Canine { public abstract Bark speak(); } This option is incorrect because the class "Canine" is not declared as abstract, but it contains an abstract method "speak()". Abstract methods can only exist in abstract classes.

Option D) public class Canine abstract { public abstract Bark speak(); } This option is incorrect because the keyword "abstract" should come before the class name, not after it. The correct syntax is "public abstract class Canine".

The correct answer is B. This option is correct because it declares an abstract class "Canine" with a concrete method "speak()" that returns a "Bark" object, even though the implementation is empty.

Which is true? (Choose all that apply. )
technology programming languages

  1. X extends Y is correct if and only if X is a class and Y is an interface.

  2. X extends Y is correct if and only if X is an interface and Y is a class.

  3. X extends Y is correct if X and Y are either both classes or both interfaces.

  4. X extends Y is correct for all combinations of X and Y being classes and/or interfaces.

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Correct Option: C