add Base solution for hw4

java/wordStat/WordStat.java

@@ -1,7 +1,53 @@
-package wordStat;
+import java.io.*;
+import java.util.*;
 
 public class WordStat {
   public static void main(String[] args) {
-    System.out.println("hello world!");
+    if (args.length != 2) {
+      System.err.println("incorrect input!");
+      System.err.println("usage: java WordStat inputFile outputFile");
+    }
+
+    String inputFileName = args[0];
+    String outputFileName = args[1];
+    try {
+      BufferedReader r = new BufferedReader(new FileReader(inputFileName));
+
+      LinkedHashMap<String, Integer> wordCount = new LinkedHashMap<>();
+      StringBuilder sb = new StringBuilder();
+
+      int data = r.read();
+      while (data != -1) {
+        char c = (char) data;
+
+        if (Character.getType(c) == Character.DASH_PUNCTUATION || 
+            Character.isLetter(c) || c == '\'') {
+          sb.append(c);
+        } else {
+          if (sb.length() > 0) {
+            String word = sb.toString().toLowerCase();
+            wordCount.put(word, wordCount.getOrDefault(word, 0) + 1);
+            sb.setLength(0);
+          }
+        }
+        
+        data = r.read();
+      }
+
+      r.close();
+
+      PrintWriter writer = new PrintWriter(outputFileName, "UTF-8");
+
+      for (Map.Entry<String, Integer> entry : wordCount.entrySet()) {
+        String key = entry.getKey();
+        int value = entry.getValue();
+        writer.println(key + " " + value);
+      }
+
+      writer.close();
+
+    } catch (Exception ex) {
+      System.err.println("An error occured: " + ex.getMessage());
+    }
   }
 }