Getting a key from a hashmap through a variable

Question

Hi i am new to java i hope i could find the answer to my problem..i am tying to write a program using hashmap where i am taking input from a file containing hindi characters(Indian language)mapping each character to 1st hashmap from which i get the corresponding value(unicode value of each character) then taking that value to another hashmap from which i get corresponding value(unicode value of the same character in a different language) this should be taken to the third hash map and retrive corresponding key(Corresponding character).. The first two mapping is working fine but when making mapping to the 3rd hashmap its returning null instead of the key which is a character in kannada(Indian language).This program is to transiliterate file in one language to another.

Object x=kannadahash.get("w"); is the part i am getting null instead of the character

The code i have written:

Any other suggestion in doing this differently would also be welcome Thank you in advance..

import java.util.*;
import java.util.Properties;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
import java.util.Enumeration;
import java.util.Collections;

public class Hashmap1 {

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

                HashMap hindihash=new HashMap();
                hindihash.put("अ",905);
                hindihash.put("आ",906);
                HashMap kannadahash=new HashMap();
                kannadahash.put("ಅ","C85" );
                kannadahash.put("ಆ","C86");
                HashMap hkhash = new HashMap();
                hkhash.put(905,"C85" );
                hkhash.put(906,"C86");
                File f = new File("D:/Hello.txt");
                if (!f.exists() && f.length() < 0)
                 {
                        System.out.println("The specified file does not exist");
                 } 
                else 
                 {
                        FileReader fr = new FileReader(f);
                        BufferedReader reader = new BufferedReader(fr);
                        String st = " ";
                        while ((st = reader.readLine()) != null)
                        {
                            Object v = hindihash.get(st);  
                            Object w=hkhash.get(v);
                               if(w!=null)
                                 {
                                     System.out.println(" "+w.toString());
                                 }
                                else
                                {
                                   System.out.println("There is no key named  " +
                                    "in the HashMap.");
                                }

                             Object x=kannadahash.get("w");

                             if(x!=null)
                             {
                                 System.out.println(" "+x.toString());
                             }
                           else
                             {
                                   System.out.println("There is no key named  " +
                                   "in the HashMap.");
                             }
                        }

                     } 

                  }          

Answer 1

You've got quite a few problems going on..

First, you're missing the opening bracket in your main method.

Second, you should really use generics with your HashMaps, like this:

HashMap<String, Integer> hindihash = new HashMap<String, Integer>();

That way you don't have to worry about dealing with Objects when you use .get(); you know the HashMap will map a String value to an Integer value. Type safety is important.

Third, this if-statement will not work correctly:

if (!f.exists() && f.length() < 0)

While the length() check is not necessary, I can understand why you may want it. If the user has an empty file named "Hello.txt" then maybe you want to consider the file as nonexistant. That's fine, but f.length() returns 0 when a file does not exist, not -1. So your if-statement does not fire correctly.

Fourth, your kannadahash HashMap appears to be backwards. अ = 905. hkhash.get(905) = "C85". kannadahash.get("C85") does not exist. Perhaps you meant this:

kannadahash.put("C85", "ಅ" );

That way, hindihash.get("अ") = 905, hkhash.get(905) = "C85", and kannadahash.get("C85") returns ಅ.

Fifth, if your goal is to "transliterate" the entire file, this will not work:

while ((st = reader.readLine()) != null)

That, as you can tell, will read each line of the file at once. You want to read each character of the file individually with BufferedReader's .read() method. Alternatively, you can use a for loop to iterate through the entire line that you read in with .readLine(), but you're probably better off with just using .read() in this case.

Sixth, your debug System.out.println()'s s are missing the variable to print out, but that's not terribly important for now.

And finally, like the others have mentioned:

Object x=kannadahash.get("w");

should be

Object x=kannadahash.get(w);

You should also work on improving your variable names and spacing. It's pretty important.

Answer 2

I think it should be

Object x = kannadahash.get(w);

This is because "w" is referring to the string and not the variable w

V

Answer 3

Shouldn't kannadahash be inverted? As I understand it, you want to lookup a hindihash to get its code, then translate that code to another code using hkhash, then retrieve the appropriate character from kannadahash using the code, thus the keys of kannadahash should be the unicode values, rather than the characters. Eg:

HashMap kannadahash=new HashMap();
kannadahash.put("C85", "ಅ");
kannadahash.put("C86", "ಆ");

In addition as the other answerer noted, you are doing get("w"), however I suspect you meant Object x=kannadahash.get(w);

Answer 4

Hi this problem could be caused be to complicated logic you have implemented in your solution.

Single map is more then enough for this, the map where you store the relation between Hindi and Kannada. I am not an expert in that language and do not know about any relation from one to another. So i will focus on solution that involve a association map, where one character can be assigned to another. But you could investigate the language properties to find some better relation and probably using a array would be enough.

So the map will store only Unicode where key is Hindi (Devanagari) and value is Kannada.

Map<Intger,Integer> hindiToHannada = new HashMap<Intger,Integer>();

   hindiToHannada.put(0x905,0xC85); //0x stand for hex
   hindiToHannada.put(0x906,0xC86); //Observation 1

Then we need to read the file properly.

BufferedReader in = new BufferedReader(new InputStreamReader(stream, encoding)); 

Where stream is the file, and encoding could be "UTF-8"

You main problem is here:

Object v = hindihash.get(st); 

The st is st = reader.readLine() naturally, you do not store a line in map.

String line; 
StringBuilder newLine = new StringBuilder();

while ((line = reader.readLine()) != null) {
  newLine.delete(0,newLine.length());
  newLIne.ensureCapacity(line.length();


  for(int pos = 0; len = line.length(); pos < len; pos++) {

   char c = line.charAt(pos);

   if(isHindi(c)) {
       newLine.append(transforToHannada(c));
    } else {
       newLine.append(c);
    }
  }
}

Observation 1. For first two sign we see some correlation, they both differ in 895 in ASCII table position you should check that this rule apply to other characters. Then no map would be required but only verification that sing is Hindi (simple if ) and if true then just add 985 to it.

UTF-8 table