不使用HashSet从LinkedList删除重复项-Java

Question

I am attempting to remove a student from the linked list if the two students are the same, meaning a duplicate input. This is being tested with JUnit test cases. However, any testing is returning the same list with no students removed. This is the removeDuplicate method, where list is my linkedList.

public void removeDuplicates() {

    for (int i = 0; i < list.size()-1; i++) {
        for (int j = i + 1; j < list.size(); j++) {
            if (list.get(i).equals(list.get(j))) {
                list.remove(j);
            }
        }
    }
}

An example of one of the failing test cases:

public void test_removeDuplicates_1() {
    ISimpleDatabase model = new SimpleDatabaseModel();
    Student s1 = new Student("John Doe", "G123456789", 3.5);
    Student s2 = new Student("Paul Graham", "G123456987", 2.75);
    Student s3 = new Student("Mary Joe", "G331456987", 3.25);
    Student s4 = new Student("Martin Fowler", "G654789321", 3.65);
    Student s5 = new Student("Paul Graham", "G123456987", 2.75);
    Student s6 = new Student("Mary Joe", "G331456987", 3.25);
    model.insert(s1);
    model.insert(s2);
    model.insert(s3);
    model.insert(s4);
    model.insert(s5);
    model.insert(s6);
    model.removeDuplicates();
    String expected = s1 + "\n" + s2 + "\n" + s3 + "\n" + s4;
    assertEquals(expected,model.toString().trim());

Which returns this error:

I am certain the error is in the removeDuplicates() method, but I can't seem to figure it out. Thanks for your help.

Answer 1

If you remove an item you need to step j back one so you test the newly shuffled-down item, otherwise you will miss it.

if (list.get(i).equals(list.get(j))) {
    list.remove(j);
    j--;
}

Answer 2

I figured out something that works. I'm just checking one of the fields for duplicates because if the student id is the same, then the student is the same as well. This appears to pass all test cases now for me. Just needed some time away to figure it out. Thanks everyone.

public void removeDuplicates() {

    for (int i = 0; i < list.size() - 1; i++) {
        int count = i + 1;
        while (count < list.size()) {
            if (list.get(i).getGnumber().equals(list.get(count).getGnumber())) {
                list.remove(count);
            } else {
                count++;
            }
        }
    }
}