Tag: programming languages

Questions Related to programming languages

Given: 10. public class Fabric 11. public enum Color { 12. RED(0xff0000), GREEN(0x00ff00), BLUE(0x0000ff); 13. private final int rgb; 14. Color( int rgb) { this.rgb = rgb; } 15. public int getRGB() { return rgb; } 16. }; 17. public static void main( String[] argv) { 18. // insert code here 19. } 20. } Which two code fragments, inserted independently at line 18, allow the Fabric class to compile? (Choose two.)
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  1. Color skyColor = BLUE;

  2. Color treeColor = Color.GREEN;

  3. Color purple = new Color( 0xff00ff);

  4. if( Color.RED.ordinal() < Color.BLUE.ordinal() ) {}

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Correct Option: B,D

Given: 11. public enum Title { 12. MR(”Mr.”), MRS(”Mrs.”), MS(”Ms.”); 13. private final String title; 14. private Title(String t) { title = t; } 15. public String format(String last, String first) { 16. return title + “ “ + first + “ “ + last; 17. } 18. } 19. public static void main(String[] args) { 20. System.out.println(Title.MR.format(”Doe”, “John”)); 21. } What is the result?

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  1. Mr. John Doe

  2. An exception is thrown at runtime

  3. Compilation fails because of an error in line 12

  4. Compilation fails because of an error in line 15

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Correct Option: A

Given: 11. public static void main(String[] args) { 12. Object obj =new int[] { 1,2,3 }; 13. int[] someArray = (int[])obj; 14. for (int i: someArray) System.out.print(i +“ “) 15. } ‘What is the result?
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  1. 1 2 3

  2. Compilation fails because of an error in line 12.

  3. Compilation fails because of an error in line 13

  4. Compilation fails because of an error in line 14

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Correct Option: A
Explanation:

To solve this question, the user needs to know about arrays and casting in Java. The code initializes an Object obj to an array of integers with values 1, 2, and 3. It then casts the object to an array of integers and assigns it to the someArray variable. Finally, it uses a for-each loop to print out each element of the someArray array.

Now, let's go through each option and explain why it is right or wrong:

A. 1 2 3: This option is correct. The code initializes an array of integers with values 1, 2, and 3, casts it to an array of integers, and then prints out each element of the array using a for-each loop. This results in the output "1 2 3".

B. Compilation fails because of an error in line 12: This option is incorrect. Line 12 initializes an object to an array of integers, which is allowed in Java. There is no compilation error in this line.

C. Compilation fails because of an error in line 13: This option is incorrect. Line 13 casts the obj object to an array of integers, which is also allowed in Java. There is no compilation error in this line.

D. Compilation fails because of an error in line 14: This option is incorrect. Line 14 uses a for-each loop to print out each element of the someArray array, which is also allowed in Java. There is no compilation error in this line.

Therefore, the answer is:

The Answer is: A. 1 2 3

Given: 10. class Foo { 11. static void alpha() { /* more code here / } 12. void beta() { / more code here */ } 13. } Which two are true? (Choose two.)
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  1. Foo.beta() is a valid invocation of beta().

  2. Foo.alpha() is a valid invocation of alpha().

  3. Method beta() can directly call method alpha().

  4. Method alpha() can directly call method beta().

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Correct Option: B,C

A programmer needs to create a logging method that can accept an arbitrary number of arguments. For example, it may be called in these ways: logIt(”log message 1 “); logIt(”log message2”,”log message3”); logIt(”log message4”, “log message5”, “log message6); Which declaration satisfies this requirement?
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  1. public void logIt(String * msgs)

  2. public void logIt(String [] msgs)

  3. public void logIt(String... msgs)

  4. public void logIt(String msg1, String msg2, String msg3)

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Correct Option: C

A programmer is designing a class to encapsulate the information about an inventory item. A JavaBeans component is needed to do this. The Inventoryltem class has private instance variables to store the item information: 10. private int itemId; 11. private String name; 12. private String description; Which method signature follows the JavaBeans naming standards for modifying the itemld instance variable?
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  1. itemID(int itemId)

  2. update(int itemId)

  3. setItemId(int itemId)

  4. mutateItemId(int itemId)

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Correct Option: C
Explanation:

To solve this question, the user needs to understand the naming conventions used in JavaBeans to create setter methods for private instance variables.

According to JavaBeans conventions, setter methods for private instance variables should be named in the format setVariableName. Therefore, the correct method signature to modify the itemId instance variable in the Inventoryltem class should be:

C. setItemId(int itemId)

Option A: itemID(int itemId) is not following the JavaBeans naming standards for setter methods. The method name should start with the prefix set followed by the variable name.

Option B: update(int itemId) does not follow the JavaBeans naming conventions. The method name should start with the prefix set followed by the variable name.

Option D: mutateItemId(int itemId) is not a standard JavaBeans naming convention. The method name should start with the prefix set followed by the variable name.

Therefore, the correct answer is:

The Answer is: C. setItemId(int itemId)

Click the Exhibit button. 1. public class A { 2. 3. private int counter = 0; 4. 5. public static int getInstanceCount() { 6. return counter; 7. } 8. 9. public A() { 10. counter++; 11. } 12. 13. } Given this code from Class B: 25.A a1 =new A(); 26. A a2 =new A(); 27. A a3 =new A(); 28. System.out.printIn(A.getInstanceCount() ); What is the result?
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  1. Compilation of class A fails

  2. Line 28 prints the value 3 to System.out

  3. Line 28 prints the value 1 to System.out.

  4. A runtime error occurs when line 25 executes

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Correct Option: A

Given: 10. class One { 11. public One foo() { return this; } 12. } 13. class Two extends One { 14. public One foo() { return this; } 15. } 16. class Three extends Two { 17. // insert method here 18. } Which two methods, inserted individually, correctly complete the Three class? (Choose two.)
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  1. public void foo() { }

  2. public int foo() { return 3; }

  3. public Two foo() { return this; }

  4. public Object foo() { return this; }

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Correct Option: C,D

Given: 10. class One { 11. void foo() {} 12. } 13. class Two extends One { 14. //insert method here 15. } Which three methods, inserted individually at line 14, will correctly complete class Two? (Choose three.)

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  1. int foo() { /* more code here */ }

  2. void foo() { /* more code here */ }

  3. public void foo() { /* more code here */ }

  4. protected void foo() { /* more code here */ }

Show answer
Correct Option: B,C,D

AI Explanation

To answer this question, we need to understand the concept of method overriding and access modifiers in Java.

In Java, when a class extends another class, it inherits all the methods from the superclass. However, if the subclass needs to provide a different implementation of a method inherited from the superclass, it can override the method.

In this scenario, class Two extends class One, which means that it inherits the method foo() from class One. To correctly complete class Two, we need to override the foo() method with the correct access modifier.

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

Option A) int foo() { /* more code here */ } This option is incorrect because it changes the return type of the foo() method, which is not allowed when overriding a method.

Option B) void foo() { /* more code here */ } This option is correct because it overrides the foo() method with the same return type and access modifier.

Option C) public void foo() { /* more code here */ } This option is correct because it overrides the foo() method with the same return type and a broader access modifier (public is broader than the default access modifier).

Option D) protected void foo() { /* more code here */ } This option is correct because it overrides the foo() method with the same return type and a broader access modifier (protected is broader than the default access modifier).

The correct answers are B), C), and D). These options correctly complete class Two by overriding the foo() method with the same return type and appropriate access modifiers.

Click the Exhibit button. 1. public interface A { 2. public void doSomething(String thing); 3. } 1. public class AImpl implements A { 2. public void doSomething(String msg) { } 3. } 1. public class B { 2. public A doit() { 3. // more code here 4. } 5. 6. public String execute() { 7. // more code here 8. } 9. } 1. public class C extends B { 2. public AImpl doit() { 3. // more code here 4. } 5. 6. public Object execute() { 7. // more code here 8. } 9. } Which statement is true about the classes and interfaces in the exhibit?

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  1. Compilation will succeed for all classes and interfaces.

  2. Compilation of class C will fail because of an error in line 2.

  3. Compilation of class C will fail because of an error in line 6.

  4. Compilation of class AImpl will fail because of an error in line 2.

Show answer
Correct Option: C
Explanation:

To solve this question, users need to understand the concept of interfaces and inheritance in Java programming language.

  • The interface A declares a method called doSomething that takes a string parameter.
  • The class AImpl implements the A interface and provides an implementation for the doSomething method.
  • The class B declares a method called doit that returns an object of type A.
  • The class C extends B and declares a method called doit that returns an object of type AImpl. It also declares a method called execute that overrides the execute method in class B and returns an object of type Object.

Now let's go through each option:

A. Compilation will succeed for all classes and interfaces.

This option is incorrect. Although there are no syntax errors in the code, there is a logical error in class C. It overrides the doit method in class B with a method that returns AImpl instead of A. This violates the Liskov Substitution Principle, which states that subclasses should be substitutable for their base classes. As a result, compilation will fail for class C.

B. Compilation of class C will fail because of an error in line 2.

This option is incorrect. There are no syntax errors in line 2 of class C. The error is a logical error, as explained above.

C. Compilation of class C will fail because of an error in line 6.

This option is correct. The execute method in class C attempts to override the execute method in class B. However, the return type of the method in class C is Object, which is not a subtype of the return type of the method in class B, which is String. As a result, compilation will fail for class C.

D. Compilation of class AImpl will fail because of an error in line 2.

This option is incorrect. There are no syntax errors in line 2 of class AImpl.

Therefore, the correct answer is:

The Answer is: C. Compilation of class C will fail because of an error in line 6.