Sorting data

[yrollgayanth]

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?

[ProgrammingPup]

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.

[yrollgayanth]

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

[ProgrammingPup]

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

[yrollgayanth]

Thanx alot..you are really helpful

[AndreB]

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?

[yrollgayanth]

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

[AndreB]

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.

//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.

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:

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;
		}
		
	}