Problem sorting data in a file?

Question

I have a problem sorting this file alphabetically by second name. Basically, my method sorts each column alphabetically but i would like to sort the file according to the second name. I really really need help. Thanks
File:
Moe     Carl
Saul     Sergio
Rocky     Louis
Ike     Ziken     
This is how my method sorts the file:
Ike          Carl
Moe          Louis
Rocky          Sergio
Saul          ziken
Instead
Moe     Carl
Rocky      Louis
Saul     Sergio
Ike     Ziken
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
class thedata implements Comparable
          private String firstname;
          private String secondname;
    public void setFirstname(String firstname)
             this.firstname = firstname;
    public String getFirstname()
              return firstname;
    public void setSecondname(String secondname)
            this.secondname = secondname;
    public String getSecondname()
            return secondname;
    public int compareTo(Object Student) throws ClassCastException
            if (!(Student instanceof ShowData))
            throw new ClassCastException("Error");
            String sn = ((ShowData) Student).getSecondname();
            return this.secondname.compareTo(sn);
public class sort {
        public static void main(String[] args) {
        sortmethod();
        public static void sortmethod(){
          int j = 0;
          thedata data[] = new thedata[4];
         try
                  FileInputStream fstream = new FileInputStream("datafile.txt");
                  DataInputStream in = new DataInputStream(fstream);
                  BufferedReader br = new BufferedReader(new InputStreamReader(in));
                  String line;
                  String[] firstname = new String[4];
                  String[] secondname = new String[4];
                  ArrayList<String> list = new ArrayList<String>();
                  while ((line = br.readLine()) != null)
                          list.add(line);
                  Iterator<String> itr = list.iterator();
                  int k = 0;
                  for (itr = list.iterator(); itr.hasNext();)
                          String str = itr.next().toString();
                          String[] splitSt = str.split("\t");
                 for (int i = 0; i < splitSt.length; i++)
                             firstname[k] = splitSt[0];
                             secondname[k] = splitSt[1];
                  k++;
                  arraysort(firstname);
                  arraysort(secondname);
                     for(j = 0;j < 4;j++)
                             data[j] = new thedata();
                             data[j].setFirstname(firstname[j]);
                             data[j].setSecondname(secondname[j]);
                  for (int i = 0; i < 4; i++)
                             thedata show = data;
                         String firstname1 = show.getFirstname();
                         String secondname1 = show.getSecondname();
                              System.out.println(firstname1 + "\t\t" + secondname1);
                    catch (Exception e)
     private static void arraysort(String[] array)
          for(int i=0; i<array.length; i++)
               for(int j=0; j<array.length-1-i; j++)
                    if(array[j].compareTo(array[j+1])>0)
                              String temp1 ="";
temp1= array[j];
array[j] = array[j+1];
array[j+1] = temp1;
Edited by: 999363 on Apr 11, 2013 3:41 AM

Answer 1

You're not sorting your objects, you're only sorting the firstname and secondname arrays separately, so they get scrambled. Sort the array of `thedata` objects.
BTW this:
    public int compareTo(Object Student) throws ClassCastException
            if (!(Student instanceof ShowData))
            throw new ClassCastException("Error");
            String sn = ((ShowData) Student).getSecondname();
    }contains a complete waste of time. You should just remove 'throws ClassCastException' and the first two lines of the method. The test and throw happens anyway at the cast. If Student isn't an instance of ShowData the cast will fail with the same exception (and a much better error message).