started alpha char

src/main/java/rocks/zipcode/AlphaCharDocument.java

 package rocks.zipcode;
 
-import java.io.IOException;
+import java.io.*;
 
 /**
  * @author leon on 16/11/2018.
  */
 public class AlphaCharDocument extends Document {
+
+private FileWriter fw;
+private String fileName;
+private File file = new File(fileName);
+
     public AlphaCharDocument(String fileName) throws IOException {
         super(fileName);
+        this.fileName = fileName;
+        fw = new FileWriter(fileName);
     }
 
     @Override
     public void write(String contentToBeWritten) {
+        try {
+            isAlpha(contentToBeWritten);
+            fw.write(contentToBeWritten);
+        } catch (IOException ex) {
+            ex.printStackTrace();
+        }
     }
 
-    private Boolean isAlpha(String s) {
+    public String read() throws FileNotFoundException {
+        BufferedReader br = new BufferedReader(new FileReader(file));
+        try {
+            return br.readLine();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
         return null;
     }
+
+    private void isAlpha(String s) throws IOException {
+        if(!s.matches("[a-zA-Z\\s]*"))
+            throw new IllegalArgumentException();
+    }
 }

src/main/java/rocks/zipcode/Document.java

     }
 
     @Override
-    public String read() {
+    public String read() throws FileNotFoundException {
         return null;
     }
 

src/main/java/rocks/zipcode/DocumentInterface.java

 package rocks.zipcode;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.util.List;
 
 /**
 
     String read(Integer lineNumber);
 
-    String read();
+    String read() throws FileNotFoundException;
 
     void replaceAll(String stringToReplace, String replacementString);
 

src/test/java/rocks/zipcode/alphadocument/AlphaDocumentWriteTest.java

         // when
         documentWriter.write(expected);
         String actual = documentWriter.read();
-
+        System.out.println(actual);
         // then
         Assert.assertEquals(expected, actual);
     }