排序数组：冒泡排序

Question

public static void sortByNumber(Course[] list) {
    Course temp = new Course();

    boolean fixed = false;

    while(fixed == false) {
        fixed = true;
    for (int i = 0; i<list.length-1; i++) {

        if (list[i].getNum() > list[i+1].getNum()) {
            temp.setNum(list[i].getNum());
            temp.setDept(list[i].getDept());
            temp.setTitle(list[i].getTitle());

            list[i] = list[i+1];
            list[i+1] = temp;
            fixed = false;
        }
    }
    }}

This is a method for sorting courses offered by university.

For example, each course has its department (ie MATH), number (ie 263) and title (ie Ordinary Differential Equations for Engineers) - MATH 263 Ordinary Differential Equations for Engineers.

In my another class, I have created an object Course, which has its own accessors and mutators (ie getNum(), setNum(), getDept(), so on).

Given a long list of courses, I wanted to arrange them according to their course numbers, but the above method does not seem to work.

Can someone hint reason for this?

Answer 1

The temp variable is a reference to a Course object.

Actually the array list is an array of references to Course objects.

You only need to change references and not copy the object's values into temp . Just do temp = list[i]; to keep a reference to the i-th element of the array.

Answer 2

I would rather implement the Comparable interface.

class Course implements Comparable<Course>{
    @Override
    public int compareTo(Course other){
        return this.getNum().compareTo(other.gerNum());
    }
}

And then you can use Array.sort(Course[] list) to sort your courses array.