Sorting data

Hello every1. I'm having a problem sorting data which reads from a text file.

Data in the text file as follows

1 334 John Steffensen AUS 44.82
2 500 Takeshi Fujiwara ESA 46.92
3 651 Dimitrios Rogas GRE 46.22
4 352 Chris Brown BAH 44.5
5 1050 Rennyuow Santa TRI 45.7
6 491 Arismendy Peguero DOM 44.92
7 897 Marcin Marciniszyn POL 45.83
8 626 Bastian Swillims GER 45.44

When program runs i want data to be sorted out in ascending order correspond to the lap time as follows.

4 352 Chris Brown BAH 44.5
1 334 John Steffensen AUS 44.82
6 491 Arismendy Peguero DOM 44.92
8 626 Bastian Swillims GER 45.44
5 1050 Rennyuow Santa TRI 45.7
7 897 Marcin Marciniszyn POL 45.83
3 651 Dimitrios Rogas GRE 46.22
2 500 Takeshi Fujiwara ESA 46.92

My code so far

import java.io.*;
import java.util.*;

public class Main {

public static class readfile{
private Scanner x;



public void openfile()throws java.io.IOException{
try{
FileReader fr = new FileReader("Lap.dat");
x = new Scanner(fr);
}
catch(Exception e){
System.out.println("Could not locate the file"+e);
}
}

public void readfile(){

int lane ;
int number ;
String firstname ;
String surname ;
String country ;
double laptime ;



while(x.hasNext()){ //as long as data contain in file

lane = x.nextInt();
number = x.nextInt();
firstname = x.next();
surname = x.next();
country = x.next();
laptime = x.nextDouble();




System.out.printf("%s %s %s %s %s %s\n",lane,number,firstname,surname,country,laptim e);







}
}


public void closefile(){
x.close();
}
}

public static void main(String[] args)throws java.io.IOException {


readfile r = new readfile();
r.openfile();
r.readfile();
r.closefile();
}

}



Can someone help me to do that please?

When you read in from the file Store each line in a HashMap with the lap time as the key. Then instead of using printf just loop through your HashMap and have it sort according to the keyValues.

ok thanx, but could you please tell me how to apply that,because I've never used it before.

HashMap (Java 2 Platform SE v1.4.2)

HashMap<Double,String> map = new HashMap<Double,String>();
while(x.hasNext()){
lane = x.nextInt();
number = x.nextInt();
firstname = x.next();
surname = x.next();
country = x.next();
laptime = x.nextDouble();

map.put(laptime,lane+number+firstname+surname+coun try+laptime);
}

Map<Double, String> sortedMap = new TreeMap<Double, String>(map);

System.out.println(sortedMap);


that looks good

Thanx alot..you are really helpful

Or you can do some generic variant:
Create a object represting a row (number, name, nationality, time) and the create an array representation of your data set.
Then you can use the Arrays.*sort* method with your object and a Compartor interface. This interface may then sort based on your preferences.
Need a code?

yes if you can give me the code that would be great..And i need only the first three results to be printed as the output as following..

4 352 Chris Brown BAH 44.5
1 334 John Steffensen AUS 44.82
6 491 Arismendy Peguero DOM 44.92

Here some sample code (far from complete, but thats your job, isn't it?)... if you have questions, ask ;-)

The sorting calss would look like this.

Code:

---

//read data... translate to objects...
//create array (from list or something other)
Result[] myArray = {new Result()};

// sorting given a reusable sorter (own implementation)               
Arrays.sort(myArray, new MySorter(MySorter.SortIndicator.time, -1));
               
// or as anonymous class (sorting by time)
//note, that the sorting happens on the given reference.
//no new object array will be returned and the old sorting gets lost
Arrays.sort(myArray, new Comparator<Result>() {
        @Override
        public int compare(Result o1, Result o2) {
                int result = 0;
                if (o1.getTime() > o2.getTime()) {
                        result = 1;
                } else if (o1.getTime() < o2.getTime()) {
                        result = -1;
                }
                return result;
        }
});

---

The class "Result" describes your data. Provide getter (and maybe setter) and a toString method for your object.

Code:

---

public static class Result {
                // note that atomic types also should be objects
                private String name;
               
                private Integer number1;
                private Integer number2;
                private String nationality;
                private Double time;
               
                public Double getTime() {
                        return time;
                }
               
                public String getName() {
                        return name;
                }
               
                //create getter/setter
               
                //create a suitable to string method ;-)
        }

---

And the core: the Sorter calss ;)
It implements the Comparator interface needed.

Only needed if you plan to write a clean code and improve reusability ... like all programmers should :rolleyes:

Code:

---

public static class MySorter implements Comparator<Result> {
               
                //what column to sort ?
                public static enum SortIndicator {
                        name,
                        number1,
                        number2,
                        nationality,
                        time
                }
               
                private SortIndicator indicator;
                // in what sort direction? (-1 = downwards / 1 = upwards)
                private int sortDirection;
               
                public MySorter(SortIndicator indicator, int dir) {
                        this.indicator = indicator;
                        this.sortDirection = dir;
                }

               
                @Override
                public int compare(Result o1, Result o2) {
                        int result = 0;
                        // based on what we want to compare we have to get different values
                        // if the returned objects additionally provide compareTo method the better!
                        switch (indicator) {
                        case time:
                                if (o1.getTime() > o2.getTime()) {
                                        result = 1;
                                } else if (o1.getTime() < o2.getTime()) {
                                        result = -1;
                                }
                                break;
                        case name:
                                result = o1.getName().compareTo(o2.getName());
                                break;
                        case nationality:
                                // ...
                        case number1:
                        case number2:
                        default:
                                break;
                        }
                        return sortDirection*result;
                }
               
        }

---