使用不带Array.sort的SelectionSort按字母顺序对数组排序

Question

I am referencing my code to mathebits website on SelectionSorting, changing the variables accordingly from int to String for my case, and adding in sort by alphabetical order as well.

Below is my current code for SelectionSort of students by lastName :

public static void SelectionSort(Student[] st) {
        int i, j, first;
        String temp;
        String jLastName = "";
        String firstLastName = "";
        String iLastName ="";
        for (i = st.length - 1; i > 0; i--) {
            first = 0;   
            for (j = 1; j <= i; j++) 
            {
                if (st[j].getLastName() != null) {

                    jLastName=st[j].getLastName();

                    if (st[first].getLastName() != null) {

                        firstLastName = st[first].getLastName();

                        if ((jLastName.compareToIgnoreCase(firstLastName)) > 0) {
                            first = j;
                        }
                    }
                }
            }

            iLastName = st[i].getLastName();
            temp = firstLastName;
            firstLastName = iLastName;
            iLastName = temp;
        }
    }

The code does not give me error. However, the output does not show that it has been sorted according to alphabetical order.

Answer 1

You cant compare two String like number, instead use compareTo method in String like:

if (st[..].getLastName().compareTo(..) < 0) {..

Also to change value, you need to have new Setter method in Student like:

public void setLastName(String name) {
    this.name = name;
} 

And then you could call it like:

st[..].setName(st[i].getName());