Tag: programming languages

Questions Related to programming languages

class C1 { static class C2 { static int i1; } public static void main(String a[]) { System.out.println(C1.C2.i1); } } What is the result of attempting to compile and run the program?
technology programming languages

  1. prints 0

  2. Compile time error

  3. Runtime exception

  4. None of the above

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Correct Option: A

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

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

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

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

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

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Correct Option: B
Explanation:

To solve this question, the user needs to know the syntax for declaring abstract classes in Java.

Option A: This is not a valid declaration of an abstract class, as it tries to define a method called speak that returns a Bark object, without defining the Bark class or interface. Additionally, it does not declare the class as abstract.

Option B: This is a valid declaration of an abstract class, as it declares the class as abstract using the abstract keyword, and defines an abstract method called speak that returns a Bark object. However, it does not provide an implementation for the method, which makes the class abstract.

Option C: This is not a valid declaration of an abstract class, as it tries to declare an abstract method within a non-abstract class. The class must be declared abstract for it to contain abstract methods.

Option D: This is not a valid declaration of an abstract class, as it tries to declare the class as abstract using the abstract keyword after the class name. The correct syntax is to use abstract before the class name.

Therefore, the correct answers are:

The Answer is: B.

Which are legal declarations?
technology programming languages

  1. short x [];

  2. short [] y;

  3. short [5] x2;

  4. short z2 [5];

  5. short [] z [] [];

  6. short [] y2 = [5];

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Correct Option: A,B,E

Which is true? (Choose all that apply. )

technology programming languages

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

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

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

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

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Correct Option: C

AI Explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) "X extends Y" is correct if and only if X is a class and Y is an interface - This option is incorrect. In Java, the keyword "extends" is used to indicate that a class is inheriting from another class or implementing an interface. Therefore, "X extends Y" is correct if X is a class and Y is either a class or an interface.

Option B) "X extends Y" is correct if and only if X is an interface and Y is a class - This option is incorrect. In Java, interfaces cannot directly inherit from classes. Instead, they can extend other interfaces. Therefore, "X extends Y" is incorrect if X is an interface and Y is a class.

Option C) "X extends Y" is correct if X and Y are either both classes or both interfaces - This option is correct. In Java, both classes and interfaces can extend other classes or interfaces. Therefore, "X extends Y" is correct if X and Y are either both classes or both interfaces.

Option D) "X extends Y" is correct for all combinations of X and Y being classes and/or interfaces - This option is incorrect. As mentioned before, interfaces cannot directly extend classes in Java. Therefore, "X extends Y" is not correct if X is an interface and Y is a class.

The correct answer is C. "X extends Y" is correct if X and Y are either both classes or both interfaces.

Given: 1. class Voop { 2. public static void main(String [] args) { 3. doStuff(1); 4. doStuff(1, 2); 5. } 6. // insert code here 7. } Which, inserted independently at line 6, will compile? (Choose all that apply.)
technology programming languages

  1. static void doStuff(int... doArgs) { }

  2. static void doStuff (int [] doArgs) { }

  3. static void doStuff(int doArgs...) { }

  4. static void doStuff(int... doArgs, int y) { }

  5. static void doStuff(int x, int... doArgs) { }

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Correct Option: A,E

Given the following, 1. interface Base { 2. boolean m1 (); 3. byte m2(short s); 4. } Which code fragments will compile? (Choose all that apply.)
technology programming languages

  1. interface Base2 implements Base { }

  2. abstract class Class2 extends Base { public boolean ml() { return true; } }

  3. abstract class Class2 implements Base { }

  4. abstract class Class2. implements Base { public boolean m1() { return (true); } }

  5. class Class2 implements Base { boolean m1( ) { return false; } byte m2(short s) { return 42; } }

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Correct Option: C,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(); }

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Correct Option: B

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.

Show answer
Correct Option: C

Given: 1. class Voop { 2. public static void main(String [] args) { 3. doStuff(1); 4. doStuff(1, 2); 5. } 6. // insert code here 7. } Which, inserted independently at line 6, will compile? (Choose all that apply.)
technology programming languages

  1. static void doStuff(int... doArgs) { }

  2. static void doStuff (int [] doArgs) { }

  3. static void doStuff(int doArgs...) { }

  4. static void doStuff(int... doArgs, int y) { }

  5. static void doStuff(int x, int... doArgs) { }

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Correct Option: A,E

Which are legal declarations? (Choose all that apply. )
technology programming languages

  1. short x [];

  2. short [] y;

  3. short [5] x2;

  4. short z2 [5];

  5. short [] z [] [];

  6. short [] y2 = [5];

Show answer
Correct Option: A,B,E