How to search for data within a file hosted on a web server?

You should not get a ArrayIndexOutOfBoundsExceptionin the indicated line, because in this line there is no method that could throw one.

If you change this code:

        while((line = reader.readLine())!= null) {
            if(line.indexOf(";")!= -1){
                if (line.split(";")[0].equalsIgnoreCase(request)) {
                    System.out.println("Se encontro la palabra "+ request);
                }
            }
        }

by

        while((line = reader.readLine())!= null) {
            String token0 = line.split(";",-1)[0]; // agrega el limite
            if (token0.equalsIgnoreCase(request)) {
                System.out.println("Se encontro la palabra "+ request);
            }
         }

You should get an array of size > 0 for sure.

In the search with split, a limit n > 0 limits the number of results to n , a limit of n=-1 gives you all possible results with a minimum of the entire String if the pattern is not found. n=0 behaves like n=-1 with the difference that strings are eventually discarded.

So far I can't reproduce one ArrayIndexOutOfBoundswith any of the lines of code in the indicated part, using permutations of String without ";" even "".

Seeing as I can't reconstruct the error, let's use safer code:

        while((line = reader.readLine())!= null) {
            System.out.println(String.format("in> \"%s\"",line));
            String[] token = line.split(";",-1); // agrega el limite
            if (token.length>0 && token[0].equalsIgnoreCase(request)) {
                System.out.println("Se encontro la palabra "+ request);
            }
         }

To search for the word in up to 3 words separated by ";" you use:

        while((line = reader.readLine())!= null) {
            System.out.println(String.format("in> \"%s\"",line));
            String[] token = line.split(";",-1); // agrega el limite
            int len = Math.min(token.length, 3); // max 3 palabras
            for (int i = 0; i<len;i++){
                if (token[i].equalsIgnoreCase(request)) {
                    System.out.println("Se encontro la palabra "+ request);
                }
            }
         }

Update

With the update of the question with clarification that is sought, the necessary code is changed a bit:

package prueba.de.buscar.dentro.de.un.archivo;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class PruebaDeBuscarDentroDeUnArchivo {
    /**
    * @param args the command line arguments
    */
    public static void main(String[] args) {
        // TODO code application logic here
        java.util.Scanner scanner = new Scanner(System.in);
        System.out.println("Introduce una cadena de texto a buscar: ");
        String request = scanner.next();
        // aquí tenemos que extraer hasta tres palabras que hay que buscar
        // en cada línea del archivo
        // se coloca un limite de 4 para luego considerar max 3 resultados
        // en caso de 3 ";" el resto de la entrada se encuentra en busqueda[3]
        String[] busqueda = request.split(";",4);
        try {
            final BufferedReader reader = new BufferedReader(
                new FileReader("C:\\Users\\ProKode\\Downloads\\archivo.txt")
            );
            String line = "";
            int len = Math.min(busqueda.length,3); // busquemos max 3 palabras
            // convertimos las palabras de busqueda a mínusculas para permitir busqueda ignorando "case"
            for (int i = 0, i < len; i++){ busqueda[i] = busqueda[i].toLowerCase().trim(); }   
            while((line = reader.readLine())!= null) {
                // aquí tenemos que buscar las palabras en un bucle
                for (int i = 0 ; i < len; i++)            
                    int pos = line.toLowerCase().indexOf(busqueda[i]);
                    if (pos > -1) {
                        System.out.println("Se encontro la palabra "+
                            line.substring(pos,pos + busqueda[i].length()));
                    }
                }
            }
            reader.close();
        } catch (FileNotFoundException e) {e.printStackTrace();
        } catch (IOException           e) {e.printStackTrace();}
    }
}

I implemented the solution using the methods you also used ( splitand indexOf). There was an alternative of processing the lines of your file with a regular expression using Patternand Matcherwhich would be a bit more elegant (based on feedback).

I think it would be easier if you directly look up the words on each line. Instead of:

if(line.indexOf(";")!= -1){                
    if (line.split(";")[0].equalsIgnoreCase(request)) {                 
        System.out.println("Se encontro la palabra "+ request);                    
    }
}

Try this:

String words = word1 + ";" + word2 + ";" + word3;
if(line.indexOf(words) > -1){                
    System.out.println("Se encontro la palabra "+ request);                    
}

java.lang.ArrayIndexOutOfBoundsExceptionmeans that you tried to access an array position that does not exist (a negative number, or a number greater than the size of the array - 1 ^* )

The index you tried to access is 0, which means that the array has no elements ( line.split(";").length == 0). This happens because the line simply doesn't have any ";" (possibly you have a blank line at the end of the file).

The most normal thing would be to check those conditions; for instance.

• Other than a blank line ( !line.trim().isEmpty()) before doing the split.
• Save the result of the split in an array String[] palabras = line.split(";");and check its size ( palabras.length > 0) before trying to access element 0.

In both cases, you should decide how the program will behave: you can either just ignore the line or inform the user of a runtime error ("Found a line without ';', line content is " + line).