Lexicographic sorting in Java creating a strange order

Question

I am trying to sort an object array by the names that are inside of the array.

grades[].name

I am using an insertion method with lexicographic sorting using compareTo and it is sort of working so I know I am using the compareTo correctly but not all the name is being moved correctly and I am not sure if it is my understanding of the way lexicographic works or if my loop is causing the issue. I know lexicographic compares each letter by itself to determine the place. I originally thought it just gave the string a numeric value and was looking for a way to find that but I don't think that was the case. I have looked at the other questions in regards to how this sorting works but it doesn't seem to shed any light on my issue. I would like to know if my issues is the loop, my understanding of the sorting method or something else cause this output issue.

I have 3 classes. The object calling the .insert method is a reference to class that contains my actually array so that the array can remain private.

   `GradeArray gradeArr = new GradeArray();

    gradeArr.insert("Evans", 78, courseID);
    gradeArr.insert("Smith", 77, courseID);
    gradeArr.insert("Yee", 83, courseID);
    gradeArr.insert("Adams", 63, courseID);
    gradeArr.insert("Hashimoto", 91, courseID);
    gradeArr.insert("Stimson", 89, courseID);
    gradeArr.insert("Velasquez", 72, courseID);
    gradeArr.insert("Lamarque", 74, courseID);
    gradeArr.insert("Vang", 52, courseID);
    gradeArr.insert("Creswell", 88, courseID);`

this is to make the entries in the array.

Here is my sorting loop.

`  public String reportgrades() //this is grade sorted by name 
    {
        String output = "Sorted by name ";
        int in, out;
        StudentGrade temp; //this is to hold the orginal variable. 
        //for the first letter cycle
        for (out = 1; out < nElems; out++) {
            temp = grades[out];
            in = out;
            while (in > 0 && 0 < (grades[in - 1].name.compareTo(grades[in].name))) {
                grades[in] = grades[in - 1];
                in--;
            }
            grades[in] = temp;
        }
        for (int j = 0; j < nElems; j++) {
            output += grades[j].name + ", ";
        }
        return output;
    }`

The output this is creating is Sorted by name Evans, Smith, Adams, Hashimoto, Stimson, Velasquez, Lamarque, Vang, Creswell, Yee,

I am confused as to why Evans and Smith are before Adams. I have tried to look at the docs for the way compareTo works but I didn't seem to see anything that would give me any information on it.

Answer 1

There is a problem with the algorithm when you shift the values. You need to put grades[in-1] = temp; inside your while statement in order to the shift work. I did not use a GradeStudent just a String but you can adapt. The grades array was just for an example.

public static String reportgrades() //this is grade sorted by name 
    {

    String[] grades = {"Evans", "Smith", "Adams", "Hashimoto", 
    "Stimson", "Velasquez", "Lamarque", "Vang", "Creswell", "Yee"};
    String output = "Sorted by name ";
    int in, out;
    String temp; //this is to hold the orginal variable. 
    //for the first letter cycle
    long nElems = grades.length; 
    for (out = 1; out < nElems; out++) {
        in = out;
        while (in > 0 &&  0 < (grades[in - 1].compareTo(grades[in]))) {
            temp = grades[in];
            grades[in] = grades[in-1];
            grades[in-1] = temp;
            in--;
        }    
    }
    for (int j = 0; j < nElems; j++) {
         output += grades[j] + ", ";
    }
    return output;
}