You are using Java, which is an object-oriented programming language. This means you can think about your problem in terms of classes which represent state in your problem domain and have behavior (methods) which manipulate this state.
In this case your code shows several responsabilities, for which you could create useful classes and/or methods:
- entering data via the command line (number of students, name and grade and desired sorting direction)
- a registry of students with a fixed size
- sorting the student registry in the desired direction
Class names that come to mind are: DataEntry, Student, StudentRegistry. For sorting the students in different ways the standard approach is creating a Comparator class, see below.
The classes could look roughly like this:
public class Student {
private String name;
private Double grade;
// getters and setters ommitted for brevity
}
The registry:
public class StudentRegistry {
// it's easier to use a List because you are adding students one by one
private List<Student> students;
public StudentRegistry(int capacity) {
// ...constructor code initializes an instance of StudentRegistry
}
public void addStudent(Student student) {
// add a student to the list
}
public Student[] getStudents(Comparator<Student> comparator) {
// sort the list using the comparator and Collections.sort()
// use List.toArray() to convert the List to an array
// alternatively (java 8) return a Stream of Students
// or return an unmodifiable List (using Collections.unmodifiableList())
// you don't want to expose your modifiable internal List via getters
}
}
A comparator which can sort Ascending or Descending. You could consider adding the capability to sort either by grades or by names, that would be quite easy.
public class StudentComparator implements Comparator<Student> {
public enum Direction {
ASCENDING, DESCENDING
}
// optional addition:
//public enum Field{
// NAME, GRADE
//}
// if used, add Field parameter to the constructor
public StudentComparator(Direction direction) {
// initialize instance
}
@Override
public int compare(Student a, Student b) {
// implement Comprator method, see JavaDoc
}
@Override
public boolean equals(Object o) {
// implement equals, see JavaDoc
}
}
Class for letting the user enter data:
public class DataEntry {
public int getNumberOfStudents() {
// ...
}
public Student getStudent() {
// ...
}
public StudentComparator.Direction getSortingDirection() {
// ...
}
}
And a main class:
public class Main {
public static void main(String[] args) {
DataEntry dataEntry = new DataEntry();
int capacity = dataEntry.getCapacity();
StudentRegistry studentRegistry = new StudentRegistry(capacity);
for(int i=0; i<= capacity; i++) {
studentRegistry.addStudent(dataEntry.getStudent());
}
StudentComparator comparator = new StudentComparator(dataEntry.getSortingDirection());
Student[] students = studentRegsitry.getStudents(comparator);
}
}
This approach separates concerns of your problem in separate classes and methods, making the code much easier to understand, debug and test.
For example, to test the Main class you could set up a mock DataEntry class which provides predetermined values to your test. See the topic of unit testing.
