Anyone know How to solve this basic problem?

[Anthony Alexander]

Outline
-------
My java program saves the words from ten text files into a tree map called frequencyData (it also records the frequency of each word).

There is a for loop to read each document file and the names of each file are stored in a string array (Docs).

Question
--------
How can I change the program so that a tree map is made for each document file? [I'm guessing a will have to create a new tree map within the for loop.]

Also, How do I determine the name of each new tree map? (eg. frequencyData1, frequencyData2....frequencyData10)

    
// Run.java
// --------
// At the moment all terms from 10 documents are
// saved into one tree map (frequencyData)
//
// How do I create a new tree map for each document?
//
// How do I have frequencyData1, frequencyData2 ....
// frequencyData10?
 

import java.util.*;  // Provides TreeMap, Iterator, Scanner
import java.io.*;    // Provides FileReader, FileNotFoundException
 
public class Run
{
   public static void main(String[ ] args)
   {
// **THIS CREATES A TREE MAP**
      TreeMap<String, Integer> frequencyData = new TreeMap<String, Integer>( );
 
      readWordFile(frequencyData);
      printAllCounts(frequencyData);
   }
 

   public static int getCount
   (String word, TreeMap<String, Integer> frequencyData)
   {
      if (frequencyData.containsKey(word))
      {  // The word has occurred before, so get its count from the map
   return frequencyData.get(word); // Auto-unboxed
      }
      else
      {  // No occurrences of this word
         return 0;
      }
   }
 

   public static void printAllCounts(TreeMap<String, Integer> frequencyData)
   {
      System.out.println("-----------------------------------------------");
      System.out.println("    Occurrences    Word");
 
      for(String word : frequencyData.keySet( ))
      {
         System.out.printf("%15d    %s\n", frequencyData.get(word), word);
      }
 
      System.out.println("-----------------------------------------------");
   }
 

   public static void readWordFile(TreeMap<String, Integer> frequencyData)
   {
      Scanner wordFile;
      String word;     // A word read from the file
      Integer count;   // The number of occurrences of the word
 
//**FOR LOOP TO READ THE DOCUMENTS**
for (int x=0; x<Docs.length; x++)
{ //start of for loop [*
 
      try
      {
         wordFile = new Scanner(new FileReader(Docs[x]));
      }
      catch (FileNotFoundException e)
      {
 System.err.println(e);
 return;
      }
 
      while (wordFile.hasNext( ))
      {
          // Read the next word and get rid of the end-of-line marker if needed:
  word = wordFile.next( );
 
  // This makes the Word lower case.
  word = word.toLowerCase();
 
   // Get the current count of this word, add one, and then store the new count:
        count = getCount(word, frequencyData) + 1;
        frequencyData.put(word, count);
      }
 
     } //End of for loop *]
   }
 

// Array of documents
static String Docs [] = {"words.txt", "words2.txt","words3.txt", "words4.txt",
"words5.txt", "words6.txt","words7.txt", "words8.txt",
"words9.txt", "words10.txt",};
}
 

[Ernest Friedman-Hill]

This "how do I determine the variable name" thing is a fundamental milestone that all thinking programmers get to -- some earlier, some later. The fact that you see the problem, and are trying to find a solution, is a good sign!

In any case, the important thing is that there is no solution, at least not the kind you're looking for. You can't invent variables at runtime. The compiler has to know the name of a variable, which means you have to know the name while you're typing the program -- and since you don't, for example, know how many files will be read, you don't know the names.

Now, the good news is that all it takes is looking at the problem from a slightly different angle, and I think when I say this you will slap your forehead at its obviousness: the solution to the "how do I make up variable names at runtime" question is always "use a Collection." Use, in your case, a List of Maps -- or perhaps a Map of Maps, with the filenames as keys and the word maps as the values. Then each Map has a "name" in the form of its key in the map.