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Die Methoden setDates und setTimes haben als Vorbedingungen, dass keines ihrer Argumente null ist. Dies soll anhand einer Assertion überprüft werden. (Das bedeutet, dass, wenn die Voraussetzung nicht erfüllt ist, wird das Programm an der Behauptung fehl, und ein AssertionError wird geworfen werden.)Mit Bestätigung prüfen
hier ist mein Code:
public class Section
{
/**
* Default section number.
*/
private static final String DEFAULT_SECTION_NUMBER = "";
/**
* Constant for building Strings with newline characters within them.
*/
private static final String LINE_SEPARATOR = System.
getProperty("line.separator");
/**
* The maximum number of students permitted into a section.
*/
private static final int MAXIMUM_STUDENTS_PER_SECTION = 30;
/**
* Valid length for a sectionNumber string.
*/
private static final int SECTION_NUMBER_LENGTH = 3;
/**
* Shared variable for keeping count of the number of section objects in
* existence.
*/
private static int count = 0;
/**
* The date at which the section is finished.
*/
private Date endDate;
/**
* The end time for the meeting of the section.
*/
private Time2 endTime;
/**
* The list of students in the class. This declaration uses the Java 7 facility
* of not repeating the generic type if that type can be inferred by the
* compiler.
*/
private final List<Student> roster = new ArrayList<>();
/**
* The three-character designation of the section (called a
* “number”).
*/
private String sectionNumber = DEFAULT_SECTION_NUMBER;
/**
* The date on which the section starts to meet.
*/
private Date startDate;
/**
* The time of day at which the section meets.
*/
private Time2 startTime;
/**
* The course of which this is a section.
*/
private final Course thisCourse;
/**
* Constructor.
*
* @param course the course of which this is a section
* @param sectionNumber the section number (within the course) of this section
* @throws SectionException
*/
public Section(Course course, String sectionNumber) throws SectionException
{
/* Increment the collective count of all Section objects that have been
created. Do this first as the object already exists. */
++count;
this.thisCourse = course;
try
{
if(isValidSectionNumber(sectionNumber))
this.sectionNumber = sectionNumber;
}
catch (Exception ex)
{
throw new SectionException("Error in constructor", ex);
}
}
/**
* Add a student to the course.
*
* @param student the student object to be added. If the course is full, the
* student is not added
*/
public void addStudent(Student student)
{
if(roster.size() != MAXIMUM_STUDENTS_PER_SECTION)
roster.add(student);
}
/**
* Get details about the current state of this section, including the course of
* which it is part, the dates it starts and ends, times, etc., and the current
* count of the enrollment.
*
* @return the section details
*/
public String getDetails()
{
return String.join(LINE_SEPARATOR,
"Section: " + this.toString(),
"Course: " + thisCourse.getDetails(),
"Dates: " + startDate + " to " + endDate,
"Times: " + startTime + " to " + endTime,
"Enrollment: " + roster.size());
}
/**
* Create a string that represents the information about the students in the
* course.
*
* @return a string that represents the information about the students in the
* course
*/
public String getRoster()
{
/* The following commented-out code is the obvious way to do this, using
String concatenation (and this is acceptable). However, the recommended
Java approach to this kind of operation is to use a StringJoiner (new
class in Java 8), as this uses less garbage collection resources. */
// String result = "";
// for(Student student : roster)
// {
// result += (result.isEmpty() ? "" : LINE_SEPARATOR) + student;
// }
// return result;
StringJoiner stringJoiner = new StringJoiner(LINE_SEPARATOR);
for(Student student : roster)
stringJoiner.add(student.toString());
return stringJoiner.toString();
}
/**
* Get a count of the number of students registered (on the roster) for this course.
*
* @return a count of the number of students registered for this course
*/
public int getRosterCount()
{
return roster.size();
}
/**
* Get the section number for this course.
*
* @return the section number for this course
*/
public String getSectionNumber()
{
return sectionNumber;
}
/**
* Set the start and end dates for the section.
*
* @param startDate the start date
* @param endDate the end date
*/
public void setDates(Date startDate, Date endDate)
{
/* There is no requirement to validate these. */
this.startDate = startDate;
this.endDate = endDate;
}
/**
* Set the start time and the end time for the meetings of the section.
*
* @param startTime the start time for meetings of the section
* @param endTime the end time for the meetings of the section
*/
public void setTimes(Time2 startTime, Time2 endTime)
{
/* There is no requirement to validate these. */
this.startTime = startTime;
this.endTime = endTime;
}
/**
* Section number (prefixed)
*
* @return Section number (prefixed)
*/
@Override
public String toString()
{
return thisCourse.toString() + "-" + sectionNumber;
}
/**
* Finalization. Reduce the instance count by 1.
*
* @throws Throwable standard interface.
*/
@SuppressWarnings("FinalizeDeclaration")
@Override
protected void finalize() throws Throwable
{
/* Decrement the count of the collective total of all Section objects. */
--count;
super.finalize();
}
/**
* Get a count of how many total Section objects are currently in existence.
*
* @return a count of how many Section objects are currently in existence
*/
public static int getSectionCount()
{
return count;
}
/**
* Validate the sectionNumber string. It must be of the correct length.
*
* @param sectionNumber the sectionNumber string
* @return true if the string if valid, otherwise false
*/
private static boolean isValidSectionNumber(String sectionNumber)
{
return sectionNumber != null &&
sectionNumber.length() == SECTION_NUMBER_LENGTH;
}
}
würde ich einfach platzieren ‚assert‘ vor diesem.startDate = startDate; und so weiter??? mein Buch hat nur ein Beispiel, und es ist für einen Wert gewährleistet ist zwischen 0 und 10
dies das Beispiel meines Buch verwendet, ist:
public class AssertTest
{
public static void main(string[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter a number between 0 and 10: ");
int number = input.nextInt();
//assert that the value is >= 0 and <= 10
assert (number >= 0 && number <= 10) : "bad number: " + number;
System.out.printf("You entered %d%n", number);
}
}
so i
assert this.startDate = startDate
assert this.endDate = endDate
sagen konnte und bald?