Cannot get value from key (HashMaps, text file)

Question

I started coding recently and I got stuck for several days already. So I need to get "value" from "key", which is in table like:

    one uno
    two dos
    three tres
    four cuatro

N.B.: words are separated by tab, therefore using "/t"

and what newbie me could accomplish looks something like this:

    import java.util.*;
    import java.io.*;
    public class test {
       public static void main(String[] args)throws FileNotFoundException, IOException {  
    Scanner scanner = new Scanner(new FileReader("C:\\Users\\Admin\\workspace\\test_dict\\src\\source.txt"));

        HashMap<String,String> map = new HashMap<String,String>();

        while (scanner.hasNextLine()) {
            String[] columns = scanner.nextLine().split("\t");

            map.put(columns[0],(columns[1]));
//enter a key word
   System.out.println("Enter a word");
   String[] columns = scanner.nextLine();
//ignoring upper and lower case
          columns=columns.toLowerCase();
// returns the element associated with the key
           System.out.println(map.get(columns[])); 

    //close files
       scanner.close();
        }
       }
    }

The problem is: I want to be able to type in the console the key word and get associated value to it. eg:

Enter a word:
    one
    uno

But I can't use map.get(columns[]); and when I try map.get(columns[0]); for some weird reason it shows me columns[1] so in console i got

Enter a word:
uno
Enter a word:
dos
Enter a word:
tres
Enter a word:
cuatro

`String[] columns = scanner.nextLine()` Why do you try to reuse the variable `columns` and why do you think that `#nextLine` returns an array? *"when I try `map.get(columns[0]);` for some weird reason it shows me `columns[1]`"* Why is that weird? `Map#get` returns the value associated to the passed key and this is obviously `columns[1]`, when you pass `columns[0]`. — Tom, May 23 '16 at 09:38

score 0 · Answer 1 · answered May 23 '16 at 09:39

0

     scanner.nextLine();

the output of nextLine() is string not array of string so you need to do it like this

    String consoleInput = scanner.nextLine();
    System.out.println(map.get(consoleInput.toLowerCase()));

answered May 23 '16 at 09:39

Amer Qarabsa

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score 0 · Answer 2 · answered May 23 '16 at 09:58

There are several problems:

You tried to read the file and your input in a single while-Statement. So your translation will not be imported complete and you try already to search in it.
The type are not secure, because you are using the scanner variable for reading your file "and" the console input.

Here an example, how I tried would like to resolve it more clearly:

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

public class Test {
    public static void main(String[] args)throws Exception {

        Scanner scanner = new Scanner(new FileReader("C:\\Users\\Admin\\workspace\\test_dict\\src\\source.txt"));

        HashMap<String,String> map = new HashMap<String,String>();

        while (scanner.hasNextLine()) {
            // you are loading a String Array from file to into "columns[]"
            String[] columns = scanner.nextLine().split("\t");

            // The array of the line is splittet in inserted in your map
            map.put(columns[0],(columns[1]));

            // That is all, you have to do the input in the outside of your reading while statement

            //close files
            scanner.close();
        }

        // Using input from console: http://stackoverflow.com/questions/4644415/java-how-to-get-input-from-system-console
        String input = null;
        while ((input = getConsoleInput("Enter a word: ")) != null) {
            // Use only the input for key-Search
            System.out.println(map.get(input));
        }


    }

    // Helper method for reading input
    public static String getConsoleInput(String message) throws  IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print(message);
        String input = br.readLine();
        return input;
    }
}

That really helped me! Console showed an error at first, but I moved "scanner.close();" and put it under console input and problem resolved. Everything works perfectly now! Thank you sir! — Nurbek Kuantyrov, May 24 '16 at 08:59

Cannot get value from key (HashMaps, text file)

2 Answers2