在不使用预定义排序方法的情况下用Java对arraylist进行排序

Question

I want to sort an arraylist by sales person name but I'm not allowed to use built-in sort.
In the followin code, I'm trying to manually sort it but it shows error (required: variable found: value) on the lines commented.

    int j,k;
    boolean flag = true;  
    Salesperson person = new Salesperson(null, 0, 0);

    while (flag) {
        flag = false;
        for (j = 0, k=1; j < salesperson.size()-1; j++, k++) {
            if (salesperson.get(j).getName().compareToIgnoreCase(salesperson.get(j+1).getName()) > 0) {                                             // ascending sort

                person = salesperson.get(j);
             //   salesperson.get(j) = salesperson.get(k);     
             //   salesperson.get(k) = person;
                flag = true;
            }
        }
    }

Answer 1

you can't sort an array in one loop , at least that's what i know , even if you got the part inside the if statement right , the algorithm is still wrong . You only compared each person with the adjacent person in one pass only.

Let's say you are sorting an array of numbers that looks like this :

5 4 6 3 1 2 with this algorithm , you would have this result 4 5 3 1 2 6

on one pass like you did it's still not sorted , only every number got compared to the adjacent one.

Also about setting a value , use ArrayList.set() like Eran answered .

Here are some sorting algorithms

Answer 2

//salesperson.get(j) = salesperson.get(k);     
//   salesperson.get(k) = person;

You are taking out the values through the get() method. That can't be used to assign values. That is why you get compilation errors.

What you should do is create a temp object and assigned to that and do the swapping of objects But you must recheck your sorting iteration logic

Answer 3

This is the correct code. I was making mistake in theses lines

         //salesperson.get(j) = salesperson.get(k);     
         //   salesperson.get(k) = person;

these were replaced by the following lines, and now there is no error

                salesperson.set(j, salesperson.get(k));     
                salesperson.set(k, person);

Thanks for your answers

    int j,k;
    boolean flag = true;  // will determine when the sort is finished
    Salesperson person = new Salesperson(null, 0, 0);

    while (flag) {
        flag = false;
        for (j = 0, k=1; j < salesperson.size()-1; j++, k++) {
            if (salesperson.get(j).getName().compareToIgnoreCase(salesperson.get(j+1).getName()) > 0) {                                             // ascending sort

                person = salesperson.get(j);
                salesperson.set(j, salesperson.get(k));     
                salesperson.set(k, person);
                flag = true;
            }
        }
    }