On Thu, 2009-03-19 at 14:28 -0700, Ryu wrote:
> Hi to all,
> Hope everyone is fine . I have a problem with lab as
> mentioned in subject regarding (Exercise4 : Constructor) . Actually in
> the modification it is being described that pass average as a
> parameter and created annaRecord object with newly constructor . I
> want to ask how , actually i try the things but it is of no use, I
> couldn't get the result .
>
> What I understand is that I have to pass five parameters
> to consructor including name, mathGrade, englishGrade, scienceGrade,
> and average. First i tried this.
>
> public StudentRecord(String name, double mGrade, double eGrade,
> double sGrade, double average){
> this(name, mGrade, eGrade, sGrade);
> this.average = average;
> }
>
> and in the ConstructorExample class I call it like
> this.
>
> StudentRecord annaRecord = new StudentRecord("Anna", 10, 20, 30,
> annaRecord.getAverage());
>
> but after it, it shwos the error that " variable
> annaRecord might not have been initialized ".
> why this is happened although i made a object annaRecord
> in the statement?
>
> Then I made every field of StudentRecord class static ,
> also made the getAverage() , getMath() , getEnglish(), and getScience
> methods static and try this.
>
> public StudentRecord(String name, double mGrade, double eGrade,
> double sGrade, double average){
> this(name, mGrade, eGrade, sGrade);
> this.average = average;
> System.out.println("name = " + name + " and average = " +
> average);
> }
>
> and call it like this.
>
> StudentRecord annaRecord = new StudentRecord("Anna", 10, 20, 30,
> StudentRecord.getAverage());
>
> ok there is no error but when i run the program it shows
> the output like
>
> name = Anna and average = 0.0
>
> why this show zero average ? tell me plz.
In creating an object, the Java first call its constructor.
You want to create annaRecord object by calling its constructor using
new StudentRecord with its parameters, but one of its parameter is a
method. I never knew whether such a practice is possible. Instead, I
will pass only the name and its grades (4 parameters instead of 5) and
create a method inside the constructor to calculate the average and
assign it to a field to be returned by a getter method.
You can learn more how to create a Java getter method in the tutorial.
Patrick
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