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Thread: 2 Questions about Inheritance

  1. #1
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    Default 2 Questions about Inheritance

    Hi!

    a quiz code is attached as a pdf file.

    There are 2 questions I'm not shure.

    1) Line ... is the first line of a mutator method that is inherited by the subclass.

    Answer: 17 ?

    2) Line ... is the first line of a method in the super class that is not inherited by the subclass.


    Answer 31 ?

    Am I right with my guesses?

    Thank you in advance!

    JackforJava
    Attached Files Attached Files

  2. #2
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    Default Re: 2 Questions about Inheritance

    Please post the code(wrapped in code tags)
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: 2 Questions about Inheritance

    public class Month {
    	private int name;
    	private int days;
     
    public Month(int name) {
    	setMonth(name);
    }
     
    public int getName() {
    	return(name);
    }
     
    public int getDays() {
    	return(days);
    }
     
    public void setMonth(int name) {
    	this.name = name;
    	if (name == 9 || name == 4 || name == 6 || name == 11)
    		days = 30;
    	else if(name == 2)
    		days = 28;
    	else
    		days = 31;
    }
     
    public String toString() {
    	return(this.convertToString() + " has " + days + " days in it.");
    }
     
    private String convertToString() {
    	switch (name) {
    		case 1: return "January";
    		case 2: return "February";
    		case 3: return "March";
    		case 4: return "April";
    		case 5: return "May";
    		case 6: return "June";
    		case 7: return "July";
    		case 8: return "August";
    		case 9: return "September";
    		case 10: return "October";
    		case 11: return "November";
    		case 12: return "December";
     
    		default: return "Invalid month";
    	}
    }
    }
    public class SchoolMonth extends Month {
    	private boolean holidays; // are there any holidays in this month?
    	private char semester; // 'F'all, 'S'pring, s'U'mmer
     
    	public SchoolMonth(int name) {
                super(name);
                setSemester();
                setHolidays();
            }
     
     
    	public boolean containsHolidays() {
    		return holidays;
    	}
     
     
    public void setSemester(){
    if (getName() > 7) // Aug - Dec
    semester = 'F';
    else if(getName() > 4) // May - July
    semester = 'U';
    else
    semester = 'S'; // Jan - April
    }
     
     
    public void setHolidays() {
    if (getName() != 3 && getName() !=4 && getName() != 6 && getName() !=8)
    holidays = true;
    }
     
    public String toString(){
    return (super.toString() + " It is in the " + semester + "semester.");
    }
     
     
    }

  4. #4
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    Default Re: 2 Questions about Inheritance

    The code does not use the @Override annotation so it is not easy to see what methods are being overridden.

    Also the lines are not numbered so its hard to see where the lines are you are referring to.
    What is on line 17 and 31?

    Also the posted code has lost its indentations at setSemester() ff. making it harder to read and understand.
    If you don't understand my answer, don't ignore it, ask a question.

  5. #5
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    Default Re: 2 Questions about Inheritance

    Please look at the pdf file.
    Attached Files Attached Files

  6. #6
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    Default Re: 2 Questions about Inheritance

    Sorry, I'd rather look at text posted in this thread and not have to download a file and open it.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: 2 Questions about Inheritance


  8. #8
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    Default Re: 2 Questions about Inheritance

    Please, have a look I've posted now 2 images.

  9. #9
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    Default Re: 2 Questions about Inheritance

    Can you copy the statements at lines 17 and 31 and post them with comments on why you chose them for the answers?
    If you don't understand my answer, don't ignore it, ask a question.

  10. #10
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    Default Re: 2 Questions about Inheritance

    1. public class Month {
    2. private int name;
    3. private int days;
    4. ...
    5. public Month(int name) {
    6. setMonth(name);
    7. }
    8. ...
    9. public int getName() {
    10. return(name);
    11. }
    12. ...
    13. public int getDays() {
    14. return(days);
    15. }
    16. ...
    17. public void setMonth(int name) {
    18. this.name = name;
    19. if (name == 9 || name == 4 || name == 6 || name == 11)
    20. days = 30;
    21. else if(name == 2)
    22. days = 28;
    23. else
    24. days = 31;
    25. }
    26. ...
    27. public String toString() {
    28. return(this.convertToString() + " has " + days + " days in it.");
    29. }
    30. ...
    31. private String convertToString() {
    32. switch (name) {
    33. case 1: return "January";
    34. case 2: return "February";
    35. case 3: return "March";
    36. case 4: return "April";
    37. case 5: return "May";
    38. case 6: return "June";
    39. case 7: return "July";
    40. case 8: return "August";
    41. case 9: return "September";
    42. case 10: return "October";
    43. case 11: return "November";
    44. case 12: return "December";
    45. ...
    46. default: return "Invalid month";
    47. }
    48. }
    49. }
    50. public class SchoolMonth extends Month {
    51. private boolean holidays; // are there any holidays in this month?
    52. private char semester; // 'F'all, 'S'pring, s'U'mmer
    53. ...
    54. public SchoolMonth(int name) {
    55. super(name);
    56. setSemester();
    57. setHolidays();
    58. }
    59. ...
    60. public boolean containsHolidays() {
    61. return holidays;
    62. }
    63. ...
    64. public void setSemester(){
    65. if (getName() > 7) // Aug - Dec
    66. semester = 'F';
    67. else if(getName() > 4) // May - July
    68. semester = 'U';
    69. else
    70. semester = 'S'; // Jan - April
    71. }
    72. ...
    73. public void setHolidays() {
    74. if (getName() != 3 && getName() !=4 && getName() != 6 && getName() !=8)
    75. holidays = true;
    76. }
    77. ...
    78. public String toString(){
    79. return (super.toString() + " It is in the " + semester +
    80. "semester.");
    81. }
    82. ...
    83. }


    --- Update ---

    The questions:.

    1) Line (?) is the first line of a mutator method that is inherited by the subclass.

    2) Line (?) is the first line of a method in the super class that is not inherited by the subclass.

  11. #11
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    Default Re: 2 Questions about Inheritance

    Make a list of the methods in the super class and indicate which are inherited by the subclass and which are not inherited by the subclass. Also flag the mutator methods.

    When you have that list you will be able to answer the questions.
    If you don't understand my answer, don't ignore it, ask a question.

  12. #12
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    Default Re: 2 Questions about Inheritance

    It should be:
    1) setMonth() - Line 18
    2) convertToString() - Line 32

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    Default Re: 2 Questions about Inheritance

    By any chance this exam is the Java SE 7 (number) certification? This a access modifier, private, interface @ override. Parent class and its methods are overwritten in the subclass. May share the same values used when that method is invoked or shared by other classes of that package. I didn't see the exam. Just saw the book on it.

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