Core Java MCQs (Chapterwise Multiple Choice Questions)

In your program, you need to read a zip file (myfile.zip) containing several other data files containing basic Java objects. Which of the following will allow you to construct a InputStream for the task?

new ObjectInputStream(new ZipInputStream( new FileInputStream((“myfile.zip”)));

new ZipInputStream(new ObjectInputStream(“myfile.zip”));

new ZipInputStream(new FileInputStream(“myfile.zip”));

new DataInputStream(new FileInputStream(“myfile.zip”));

Answer & Explanation

Correct Answer: new ObjectInputStream(new ZipInputStream( new FileInputStream((“myfile.zip”)));

Note: This Question is unanswered, help us to find answer for this one

Float p = new Float(3.14f); if (p > 3) { System.out.print("p is bigger than 3. "); } else { System.out.print("p is not bigger than 3. "); } finally { System.out.println("Have a nice day."); } What is the result?

p is bigger than 3. Have a nice day.

p is not bigger than 3. Have a nice day.

Compilation fails.

p is bigger than 3.

Answer & Explanation

Correct Answer: Compilation fails.

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What will be the output of the program? public class Foo { public static void main(String[] args) { try { return; } finally { System.out.println( "Finally" ); } } }

Finally

Compilation fails.

The code runs with no output.

An exception is thrown at runtime.

Answer & Explanation

Correct Answer: Finally

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Given a class containing the following pieces of code: ---------------------- public static <T> List getList() { return new ArrayList<T>(); } // ... List<?> list = new ArrayList<Integer>(); ---------------------- Adding which of the following lines would cause the class to not compile?

List<Integer> list2 = list;

All of these compile

list = getList();

list = new ArrayList<String>();

List<Integer> list2 = getList();

Answer & Explanation

Correct Answer: List<Integer> list2 = list;

Note: This Question is unanswered, help us to find answer for this one

java.util.Collection is:

An interface of non-destructive methods used by Set and List classes

An abstract interface representing a group of objects, extended by Set and List

An interface for iterable groups of objects

An abstract class representing a group of objects, extended by Set and List

Answer & Explanation

Correct Answer: An interface for iterable groups of objects

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Does interrupt() always force all threads to terminate?

Yes, after interrupt() is called a thread terminates immediatelly

No, if the interruption is not enabled for the thread, it will not terminate

Yes, the thread gets to a predefined interruption point and stops

Answer & Explanation

Correct Answer: No, if the interruption is not enabled for the thread, it will not terminate

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All of the classes in the Java Collections Framework:

Have methods to retrieve their data as an Array

Have methods allowing them to be viewed as both Maps and Lists

Involve data structures backed by Arrays

Allow elements to be added to the beginning or end of their internal List

Answer & Explanation

Correct Answer: Have methods to retrieve their data as an Array

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The data members of interface in java are:

protected final

private static

public static final

private static final

static final

Answer & Explanation

Correct Answer: public static final

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Which class/classes is/are thread safe among these?

String and StringBuffer

StringBuilder

Answer & Explanation

Correct Answer: String and StringBuffer

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The TreeMap and LinkedHashMap classes:

Enable iteration of a map's entries based on natural ordering of keys only.

Enable iteration of a map's entries based on the insertion order of elements only.

Enable iteration of a map's entries based either natural ordering of keys OR natural ordering of values - depending on the arguments sent to the constructor.

Enable iteration of a map's entries in a deterministic order.

Answer & Explanation

Correct Answer: Enable iteration of a map's entries in a deterministic order.

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Core Java Quick Quiz

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Start Practicing with our MCQs given below.