java.lang.NullPointerException, can't tell why?

Question

I'm writing a program that takes a series of words separated into tokens and reads a text, then counts their frequencies. This code has several related codes (WordCount, FreqStudy, and Echo) but the WordFreq class is what is causing the java.lang.NullPointerException error. Here is my code for WordFreq:

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

public class WordFreq extends Echo{

  WordCount[] wcArray;
  int ct;
  String[] sentence;
  double freq;
  String newLine;

  public WordFreq(String f, String words) throws IOException{
    super(f);
    String[] wordString = words.split(" ");
    for(int i=0; i<wordString.length; i++)
      wcArray[i] = new WordCount(wordString[i]);
    Scanner scan = new Scanner(new FileReader(fileName));
  }

  public void processLine(String line){
    newLine = line.toLowerCase();
    sentence = newLine.split(" "); 
    for(String s: sentence){
      for(WordCount w: wcArray){
        if(w.getWord().equals(s))
          w.incCount();
      }
      ct++;
    }     
  }

  public void reportFrequencies(){
    for (int i=0; i<wcArray.length; i++){
      freq = (wcArray[i].getCount() / ct); 
      System.out.print(wcArray[i].getWord()+" ");
      System.out.printf("%6.4f\n", freq);
    }
  }
}

And the error I recieve looks like this when I give it a file to read through the FreqStudy main class:

java.lang.NullPointerException
    at WordFreq.<init>(WordFreq.java:17)
    at FreqStudy.main(FreqStudy.java:14)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)

I really don't understand what the issue is and I've been working on this all day so I feel brain dead. Please take a look if you can, I would really appreciate it.

EDIT: I realized that I didn't initialize it right after posting this, but my frequencies return 0 results. Anyone help?

Answer 1

Initialize the array wcArray prior to assigning any values:

wcArray = new WordCount[wordString.length];