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Questions Related to programming languages

Question 6 Given: • d is a valid, non-null Date object • df is a valid, non-null DateFormat object set to the current locale What outputs the current locales country name and the appropriate version of d’s date?
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  1. Locale loc = Locale.getLocale();System.out.println(loc.getDisplayCountry()+ “ “+ df.format(d));

  2. Locale bc = Locale.getLocale();System.out.println(loc.getDisplayCountry()+ “ “+ df.setDateFormat(d));

  3. Locale loc = Locale.getDefault();System.out.println(loc.getDisplayCountry()+ “ “+ df.setDateFormat(d));

  4. Locale loc = Locale.getDefault(); System.out.println(loc.getDisplayCountry()+ “ “ + df.format(d));

Show answer
Correct Option: D
Explanation:

To solve this question, the user needs to understand the concepts of Locale, Date, and DateFormat objects.

Option A is incorrect because there is no such method as getLocale() in the Locale class. The correct method is getDefault(). Additionally, df.format(d) is used to format the date object d using the date format df. This option is incorrect because df.format(d) is called with a space between the method name and the parentheses.

Option B is incorrect because Locale.getLocale() is not a valid method in the Locale class. Also, df.setDateFormat(d) is not a valid method in the DateFormat class. Instead, df.format(d) should be used to format the Date object using the appropriate format.

Option C is incorrect because Locale.getDefault() is not used to get the current locale. Instead, Locale.getLocale() is used, which is not a valid method in the Locale class. df.setDateFormat(d) is also not a valid method in the DateFormat class. Instead, df.format(d) should be used to format the Date object using the appropriate format.

Option D is correct. Locale.getDefault() is used to get the current locale, and df.format(d) is used to format the Date object d using the appropriate date format. This option will output the current locale's country name and the appropriate version of the date object d.

Therefore, the correct answer is:

The Answer is: D

Given: 20. public class CreditCard { 21. 22. private String cardlD; 23. private Integer limit; 24. public String ownerName; 25. 26. public void setCardlnformation(String cardlD, 27. String ownerName, 28. Integer limit) { 29. this.cardlD = cardlD; 30. this.ownerName = ownerName; 31. this.limit = limit; 32. } 33. } Which is true?

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  1. The class is fully encapsulated

  2. The ownerName variable breaks encapsulation

  3. The cardlD and limit variables break polymorphism

  4. The setCardlnformation method breaks encapsulation

Show answer
Correct Option: B
Explanation:

To solve this question, the user needs to understand the concepts of encapsulation and polymorphism.

Encapsulation is the concept of hiding the implementation details of a class and making the variables and methods private to ensure that they cannot be accessed from outside the class.

Polymorphism, on the other hand, is the ability of an object to take on many forms, depending on the context in which it is used.

Now let's examine each option and determine which is true:

A. The class is fully encapsulated: This option is incorrect. While the class does have private variables (cardlD and limit), the ownerName variable is public, which means it can be accessed from outside the class. Therefore, the class is not fully encapsulated.

B. The ownerName variable breaks encapsulation: This option is correct. The ownerName variable is declared as public, which means it can be accessed and modified from outside the class. This breaks the concept of encapsulation because the implementation details of the class are not fully hidden.

C. The cardlD and limit variables break polymorphism: This option is incorrect. The cardlD and limit variables have nothing to do with polymorphism. They are private variables that can only be accessed from within the class.

D. The setCardlnformation method breaks encapsulation: This option is incorrect. The setCardlnformation method is a public method, which is used to set the values of the private variables. It does not break encapsulation because it is providing a controlled way of accessing the private variables.

Therefore, the correct answer is:

The Answer is: B

Assume that country is set for each class. Given: 10. public class Money { 11. private String country, name; 12. public getCountry() { return country; } 13.} and: 24. class Yen extends Money { 25. public String getCountry() { return super.country; } 26. } 27. 28. class Euro extends Money { 29. public String getCountry(String timeZone) { 30. return super.getCountry(); 31. } 32. } Which two are correct? (Choose two.)

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  1. Euro returns correct values

  2. An exception is thrown at runtime.

  3. Yen and Euro both return correct values

  4. Compilation fails because of an error at line 25.

Show answer
Correct Option: A,D

AI Explanation

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

Option A) Euro returns correct values - This option is correct. In the Euro class, the getCountry(String timeZone) method calls the super.getCountry() method, which is inherited from the Money class. Since the getCountry() method in the Money class does not take any arguments and simply returns the value of the country field, this method will return the correct value.

Option B) An exception is thrown at runtime - This option is not mentioned in the given code snippet. Therefore, it is incorrect.

Option C) Yen and Euro both return correct values - This option is incorrect. The Yen class overrides the getCountry() method and returns super.country. However, the super.country expression is incorrect. The country field is private in the Money class and cannot be accessed directly by the Yen class. Therefore, the Yen class will not return the correct value.

Option D) Compilation fails because of an error at line 25 - This option is correct. The Yen class attempts to access the country field of the Money class using super.country, but the country field is private and cannot be accessed from a subclass. This will result in a compilation error.

The correct answers are A and D.

Which Man class properly represents the relationship “Man has a best friend who is a Dog”?
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  1. class Man { private Dog }

  2. class Man { private BestFriend dog; }

  3. class Man { private Dog bestFriend; }

  4. class Man implements Dog { }

Show answer
Correct Option: C
Explanation:

To properly represent the relationship "Man has a best friend who is a Dog", we need to use composition to indicate that a Man object has a Dog object as its best friend.

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

A. class Man { private Dog }

This option is incorrect. The syntax used to represent the relationship between Man and Dog is incorrect. The "" does not make sense in this context.

B. class Man { private BestFriend dog; }

This option is incorrect. Although the variable name "dog" is used, it does not represent the intended relationship. The class BestFriend is not defined anywhere and doesn't make sense in this context.

C. class Man { private Dog bestFriend; }

This option is correct. The class Man has a private variable named "bestFriend" of type Dog, indicating that a Man object has a Dog object as its best friend.

D. class Man implements Dog { }

This option is incorrect. The interface Dog cannot properly represent the relationship between Man and Dog, and implementing the Dog interface does not make sense in this context.

Therefore, the correct answer is:

The Answer is: C. class Man { private Dog bestFriend; }

Given: 11. public class Person { 12. private name; 13. public Person(String name) { 14. this.name = name; 15. } 16. public int hashCode() { 17. return 420; 18. } 19. } Which is true?
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  1. The time to determine whether a Person object is contained in a HashSet is constant and does NOT depend on the size of the map

  2. Deleting a Person key from a HashMap will delete all map entries for all keys of type Person

  3. Inserting a second Person object into a HashSet will cause the first Person object to be removed as a duplicate.

  4. The time to find the value from HashMap with a Person key depends on the size of the map.

Show answer
Correct Option: D

Given: 23. Object [] myObjects = { 24. new integer(12), 25. new String(”foo”), 26. new integer(5), 27. new Boolean(true) 28. }; 29. Arrays.sort(myObjects); 30. for( int i=0; i
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  1. Compilation fails due to an error in line 23.

  2. Compilation fails due to an error in line 29.

  3. A ClassCastException occurs in line 29.

  4. A ClassCastException occurs in line 31.

Show answer
Correct Option: C
Explanation:

To solve this question, the user needs to understand the concepts of sorting arrays and the differences between the Object and Integer classes.

The code creates an array of Objects that includes Integer, String, and Boolean objects, then sorts the array using the Arrays.sort() method. Finally, the code prints out each object in the sorted array using a for loop.

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

A. Compilation fails due to an error in line 23. This option is incorrect because there are no errors in the syntax of line 23. The code creates an array of objects and initializes it with Integer, String, and Boolean objects.

B. Compilation fails due to an error in line 29. This option is incorrect because there are no errors in the syntax of line 29. The Arrays.sort() method is a valid method and can be used to sort arrays.

C. A ClassCastException occurs in line 29. This option is correct. The code attempts to sort an array of Objects, which includes Integer, String, and Boolean objects. When the sort method attempts to compare the elements in the array, a ClassCastException occurs because the elements are not all of the same type. The Integer objects are not comparable to the String and Boolean objects, resulting in an exception.

D. A ClassCastException occurs in line 31. This option is incorrect. The for loop uses the toString() method to print out each object in the array, which is a valid method for all objects. However, the exception occurs during the sort method in line 29, not during the printing of the objects.

The Answer is: C

  1. Given: 13. public class Pass { 14. public static void main(String [1 args) { 15. int x 5; 16. Pass p = new Pass(); 17. p.doStuff(x); 18. System.out.print(” main x = “+ x); 19. } 20. 21. void doStuff(int x) { 22. System.out.print(” doStuff x = “+ x++); 23. } 24. } What is the result?
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  1. Compilation fails.

  2. An exception is thrown at runtime

  3. doStuffx = 6 main x = 6

  4. doStuffx = 5 main x = 5

Show answer
Correct Option: D
Explanation:

To solve this question, the user needs to understand the basic concept of method invocation and parameter passing.

First, let's go through the code. The Pass class has a method main which initializes an integer variable x to 5. It then creates a new instance of the Pass class and invokes the doStuff method on that instance, passing in the value of x. Finally, it prints out the value of x.

The doStuff method takes an integer parameter x, prints out the value of x incremented by 1, and then increments the parameter x by 1.

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

A. Compilation fails - This option is incorrect. There are no syntax errors in the code.

B. An exception is thrown at runtime - This option is incorrect. There are no runtime errors in the code.

C. doStuffx = 6 main x = 6 - This option is incorrect. The value of x in main is still 5 after the doStuff method is called because Java is a pass-by-value language. The parameter x in doStuff is a copy of the value of x in main, so incrementing the parameter does not affect the original value of x.

D. doStuffx = 5 main x = 5 - This option is correct. The doStuff method prints out the value of x (which is 5) incremented by 1, resulting in the output "doStuff x = 6". However, the value of x in main remains 5 because Java is a pass-by-value language. Therefore, the final output is "main x = 5".

Therefore, the answer is: D. doStuffx = 5 main x = 5

Given: 10. package com.sun.scjp; 11. public class Geodetics { 12. public static final double DIAMETER = 12756.32; // kilometers 13. } Which two correctly access the DIAMETER member of the Geodetics class? (Choose two.)

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  1. import com.sun.scjp.Geodetics;public class TerraCarta {public double halfway(){ return Geodetics.DIAMETER/2.0; } }

  2. import static com.sun.scjp.Geodetics;public class TerraCarta {public double halfway() { return DIAMETER/2.0; } }

  3. import static com.sun.scjp.Geodetics. *;public class TerraCarta {public double halfway() { return DIAMETER/2.0; } }

  4. package com.sun.scjp;public class TerraCarta {public double halfway() { return DIAMETER/2.0; } }

Show answer
Correct Option: A,C

AI Explanation

To access the DIAMETER member of the Geodetics class, we need to understand the different ways to access static members.

Option A) import com.sun.scjp.Geodetics; public class TerraCarta { public double halfway(){ return Geodetics.DIAMETER/2.0; } }

This option is correct because it imports the Geodetics class and accesses the DIAMETER member using the syntax Geodetics.DIAMETER.

Option B) import static com.sun.scjp.Geodetics; public class TerraCarta { public double halfway() { return DIAMETER/2.0; } }

This option is incorrect because it tries to import the Geodetics class using the static keyword, but it does not specify which member of the class to import. Therefore, the line return DIAMETER/2.0; will cause a compilation error because DIAMETER is not recognized.

Option C) import static com.sun.scjp.Geodetics. *; public class TerraCarta { public double halfway() { return DIAMETER/2.0; } }

This option is correct because it imports all the static members of the Geodetics class using the * wildcard. Therefore, the line return DIAMETER/2.0; will correctly access the DIAMETER member.

Option D) package com.sun.scjp; public class TerraCarta { public double halfway() { return DIAMETER/2.0; } }

This option is incorrect because it does not import the Geodetics class, so the line return DIAMETER/2.0; will cause a compilation error because DIAMETER is not recognized.

Therefore, the correct answers are Option A and Option C.

Given: 10. class Nav{ 11. public enum Direction { NORTH, SOUTH, EAST, WEST } 12. } 13. public class Sprite{ 14. // insert code here 15. } Which code, inserted at line 14, allows the Sprite class to compile?14
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  1. Direction d = NORTH;

  2. Nav.Direction d = NORTH;

  3. Direction d = Direction.NORTH;

  4. Nav.Direction d = Nav.Direction.NORTH;

Show answer
Correct Option: D

Given: 10. interface Foo { int bar(); } 11. public class Sprite { 12. public int fubar( Foo foo) { return foo.bar(); } 13. public void testFoo() { 14. fubar( 15. // insert code here 16.); 17. } 18. } Which code, inserted at line 15, allows the class Sprite to compile?
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  1. Foo { public int bar() { return 1; } }

  2. new Foo { public int bar() { return 1; } }

  3. newFoo() { public int bar(){return 1; } }

  4. new class Foo { public int bar() { return 1; } }

Show answer
Correct Option: C