电话簿按字段的​​字母顺序排序

Question

I am trying to get my JavaFx application of a phone book in order to sort alphabetically the contacts list according to the first name. However, the existing loop is not listing the names in the correct order. Here is the sorting method:

 public static void sortContactList() {
        try {
        for (int i = 0; i < contactList.length - 1; i++) {
            for (int j = i + 1; i < contactList.length; j++) {
                if ((contactList[j].first.toCharArray()[0]) < (contactList[i].first.toCharArray()[0])) {
                    Entry tmp = contactList[j];
                    contactList[j] = contactList[i];
                    contactList[i] = tmp;
                }
            }
        }
    } catch (NullPointerException exc) {}
}

Below it is shown how the contact list is made up. It is stored in a file with first being the person's first names as strings:

class Entry {
public String first, last, number, note;
}
public class Phonebookfor1510 {
public static Entry[] contactList;
public static int num_entries;
public static void main(String args[]) throws Exception {
    int i;
    char C;
    String code, Command;
    contactList = new Entry[200];
    num_entries = 0;

The rest of my code works with it. I am just wondering why it is not sorting the list of values alphabetically. Any help would be greatly appreciated!!

Answer 1

The Best thing You can Do is Use TreeSet. Like the given example

TreeSet<String> stringSet = new TreeSet<>();
        stringSet.add("Mummy");
        stringSet.add("Mahima");
        stringSet.add("Gaurav");
        stringSet.add("Naresh");
        stringSet.add("Bhawna");

        for(String s : stringSet) {
            System.out.println(s);
        }

Output : Bhawna Gaurav Mahima Mummy Naresh

Answer 2

I think the second for loop will never end without a NullPointerException . You are increasing j , but checking for i<contactList .

You could use Arrays.sort() in this case.

Answer 3

take a look at this sample code:

public class Entry implements Comparable<Entry>{
    private Long id;
    private String fullName;
    private String phoneNumber;

    public int compareTo(Entry other) {
        if(other==null) throw new NullPointerException();
        /*
        -1 : phonenumber of current entry is smaller that other
        0  : phonenumber of current entry is equal to other
        +1 : phonenumber of current entry is greater than other
         */
        return (this.getFullName().compareTo(other.getPhoneNumber()));
    }
    public static void main(String[] args){
        Entry[] entriesArray = getEntriesArrayListFromSomewhere();
        Arrays.sort(entriesArray);
    }

   //getters ans setters
}