all the classes can write.

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

@@ -1,14 +1,12 @@
 package rocks.zipcode;
 
-import java.io.BufferedWriter;
-import java.io.FileWriter;
-import java.io.IOException;
+import java.io.*;
+import java.util.regex.Pattern;
 
 /**
  * @author leon on 16/11/2018.
  */
 public class AlphaCharDocument extends Document {
-    Document document;
 
     public AlphaCharDocument(String fileName) throws IOException {
 
@@ -18,15 +16,24 @@ public class AlphaCharDocument extends Document {
 
     @Override
     public void write(String contentToBeWritten) throws IOException {
-
-     
+        BufferedWriter writer = new BufferedWriter(new FileWriter("target/file.txt"));
+        writer.write(contentToBeWritten);
+        writer.close();
 
     }
 
     private Boolean isAlpha(String s) {
 
-        boolean allLetters = s.chars().allMatch(Character::isLetter);
-        return allLetters;
+//        boolean allLetters = s.chars().allMatch(Character::isLetter);
+//        return allLetters;
+
+
+//        return (s.matches("[a-zA-Z]+"));
+
+        if(! Pattern.matches(".*[a-zA-Z]+.*", s))
+            return true;
+        else return false;
+
 
     }
 

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

@@ -95,6 +95,13 @@ public class Document implements DocumentInterface {
 
     @Override
     public void overWrite(String content) {
+
+        try {
+            Writer fileWriter = new FileWriter("target/file.txt", false);
+            write(content);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
     }
 
     public List<String> toList() {

src/main/java/rocks/zipcode/NumericCharDocument.java

@@ -1,6 +1,9 @@
 package rocks.zipcode;
 
+import java.io.BufferedWriter;
+import java.io.FileWriter;
 import java.io.IOException;
+import java.util.regex.Pattern;
 
 /**
  * @author leon on 16/11/2018.
@@ -11,10 +14,15 @@ public class NumericCharDocument extends Document {
     }
 
     @Override
-    public void write(String contentToBeWritten) {
+    public void write(String contentToBeWritten) throws IOException {
+        BufferedWriter writer = new BufferedWriter(new FileWriter("target/file.txt"));
+        writer.write(contentToBeWritten);
+        writer.close();
     }
 
     private Boolean isNumeric(String s) {
-        return null;
+
+
+        return false;
     }
 }

src/main/java/rocks/zipcode/SpecialCharDocument.java

@@ -1,5 +1,7 @@
 package rocks.zipcode;
 
+import java.io.BufferedWriter;
+import java.io.FileWriter;
 import java.io.IOException;
 
 /**
@@ -11,10 +13,14 @@ public class SpecialCharDocument extends Document {
     }
 
     @Override
-    public void write(String contentToBeWritten) {
+    public void write(String contentToBeWritten) throws IOException {
+        BufferedWriter writer = new BufferedWriter(new FileWriter("target/file.txt"));
+        writer.write(contentToBeWritten);
+        writer.close();
     }
 
     private Boolean isSpecialCharacters(String s) {
+
         return null;
     }
 }