Task: Text processing_2
C#: using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.IO;

namespace TextProc2
{
    class Program
    {
        static void Main(string[] args)
        {
            Regex multiWhite = new Regex(@"\s+");
            Regex dateEx = new Regex(@"^\d{4}-\d{2}-\d{2}$");
            Regex valEx = new Regex(@"^\d+\.{1}\d{3}$");
            Regex flagEx = new Regex(@"^[1-9]{1}$");
            
            int missformcount = 0, totalcount = 0;
            Dictionary<int, string> dates = new Dictionary<int, string>();

            using (StreamReader sr = new StreamReader("readings.txt"))
            {
                string line = sr.ReadLine();
                while (line != null)
                {
                    line = multiWhite.Replace(line, @" ");                    
                    string[] splitLine = line.Split(' ');
                    if (splitLine.Length != 49)
                        missformcount++;
                    if (!dateEx.IsMatch(splitLine[0]))                        
                        missformcount++;                    
                    else
                        dates.Add(totalcount + 1, dateEx.Match(splitLine[0]).ToString());
                    int err = 0;                    
                    for (int i = 1; i < splitLine.Length; i++)
                    {
                        if (i%2 != 0)
                        {
                            if (!valEx.IsMatch(splitLine[i]))                          
                                err++;
                        }
                        else
                        {
                            if (!flagEx.IsMatch(splitLine[i]))
                                err++;                                                        
                        }                        
                    }
                    if (err != 0) missformcount++;
                    line = sr.ReadLine();
                    totalcount++;                    
                }
            }

            int goodEntries = totalcount - missformcount;
            Dictionary<string,List<int>> dateReverse = new Dictionary<string,List<int>>();

            foreach (KeyValuePair<int, string> kvp in dates)
            {
                if (!dateReverse.ContainsKey(kvp.Value))
                    dateReverse[kvp.Value] = new List<int>();
                dateReverse[kvp.Value].Add(kvp.Key);
            }

            Console.WriteLine(goodEntries + " valid Records out of " + totalcount);

            foreach (KeyValuePair<string, List<int>> kvp in dateReverse)
            {
                if (kvp.Value.Count > 1)
                    Console.WriteLine("{0} is duplicated at Lines : {1}", kvp.Key, string.Join(",", kvp.Value));                    
            }
        }
    }
}

Java: import java.util.*;
import java.util.regex.*;
import java.io.*;

public class DataMunging2 {

    public static final Pattern e = Pattern.compile("\\s+");

    public static void main(String[] args) {
        try {
            BufferedReader infile = new BufferedReader(new FileReader(args[0]));
            List<String> duplicates = new ArrayList<String>();
            Set<String> datestamps = new HashSet<String>(); 

            String eingabe;
            int all_ok = 0;
            while ((eingabe = infile.readLine()) != null) { 
                String[] fields = e.split(eingabe); 
                if (fields.length != 49) 
                    System.out.println("Format not ok!");
                if (datestamps.add(fields[0])) { 
                    int howoften = (fields.length - 1) / 2 ; 
                                                             
                    for (int n = 1; Integer.parseInt(fields[2*n]) >= 1; n++) {
                        if (n == howoften) {
                            all_ok++ ;
                            break ;
                        }
                    }
                } else {
                    duplicates.add(fields[0]); 
                }
            }
            infile.close();
            System.out.println("The following " + duplicates.size() + " datestamps were duplicated:");
            for (String x : duplicates)
                System.out.println(x);
            System.out.println(all_ok + " records were complete and ok!");
        } catch (IOException e) {
            System.err.println("Can't open file " + args[0]);
            System.exit(1);
        }
    }
}