Hi Friend,

Try the following code:

import java.io.*;
import java.util.*;
class ShowData implements Comparable {
int id;
String name;
int marks;
String grade;

public void setId(int id) {
this.id = id;
}

public int getId() {
return id;
}

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

public String getName() {
return name;
}

public void setMarks(int marks) {
this.marks = marks;
}

public int getMarks() {
return marks;
}

public void setGrade(String grade) {
this.grade = grade;
}

public String getGrade() {
return grade;
}

public int compareTo(Object Student) throws ClassCastException {
if (!(Student instanceof ShowData))
throw new ClassCastException("Error");
int ide = ((ShowData) Student).getId();
return this.id - ide;
}
}

continue..

public class SortFileData {
SortFileData() {
int j = 0;
ShowData data[] = new ShowData[5];
try {
FileInputStream fstream = new FileInputStream("C:/school.txt");
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
ArrayList list = new ArrayList();
while ((strLine = br.readLine()) != null) {
list.add(strLine);
}
Iterator itr;
for (itr = list.iterator(); itr.hasNext();) {
String str = itr.next().toString();
String[] splitSt = str.split(" ");
String id = "", name = "", marks = "", grade = "";
for (int i = 0; i < splitSt.length; i++) {
id = splitSt[0];
name = splitSt[1];
marks = splitSt[2];
grade = splitSt[3];
}
data[j] = new ShowData();
data[j].setId(Integer.parseInt(id));
data[j].setName(name);
data[j].setMarks(Integer.parseInt(marks));
data[j].setGrade(grade);
j++;
}
Arrays.sort(data);
List l=Arrays.asList(data);
Collections.sort(l).reverse(l);
File file = new File("C:/new.txt");
FileWriter fw = new FileWriter(file,true);
BufferedWriter out = new BufferedWriter(fw);
System.out.println("********Sorted by id********");
String strVal = "";
for (int i = 0; i < 5; i++) {
ShowData show = data[i];
int no = show.getId();
String name = show.getName();
int marks = show.getMarks();
String grade = show.getGrade();
System.out.println(no + " " + name + " " + marks + " "+ grade);
String d = no + " " + name + " " + marks + " " + grade;
ArrayList al = new ArrayList();
al.add(d + "\n");
Iterator itr1 = al.iterator();
while (itr1.hasNext()) {
out.write(itr1.next().toString());
out.newLine();
}
}
out.close();
} catch (Exception e) {
}
}
public static void main(String[] args) {
SortFileData data = new SortFileData();
}
}

Hope that it will be helpful for you.
Thanks