All tests passed

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

@@ -1,6 +1,9 @@
 package rocks.zipcode;
 
 import java.io.*;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.ArrayList;
 import java.util.List;
 
 /**
@@ -35,6 +38,12 @@ public class Document implements DocumentInterface {
 
     @Override
     public void write(Integer lineNumber, String valueToBeWritten) {
+
+            String line = read(lineNumber);
+            String doc = read();
+            doc = doc.replace(line, valueToBeWritten);
+            write(doc);
+
     }
 
     @Override
@@ -95,23 +104,34 @@ public class Document implements DocumentInterface {
 
     @Override
     public void replaceAll(String stringToReplace, String replacementString) {
+
+        String doc = read();
+        doc = doc.replaceAll(stringToReplace, replacementString);
+        write(doc);
+
     }
 
     @Override
     public void overWrite(String content) {
+        write(content);
     }
 
     public List<String> toList() {
-        return null;
+        String[] arr = read().split("\n");
+        List<String> result = new ArrayList<>();
+        for(String s: arr) {
+            result.add(s);
+        }
+        return result;
     }
 
     @Override
     public File getFile() {
-        return null;
+        return this.file;
     }
 
     @Override
     public String toString() {
-        return null;
+        return getFile() + "{" + read() + "}";
     }
 }

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

@@ -1,6 +1,8 @@
 package rocks.zipcode;
 
 import java.io.IOException;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * @author leon on 16/11/2018.
@@ -12,9 +14,16 @@ public class NumericCharDocument extends Document {
 
     @Override
     public void write(String contentToBeWritten) {
+        if(isNumeric(contentToBeWritten)) {
+            super.write(contentToBeWritten);
+        } else {
+            throw new IllegalArgumentException();
+        }
     }
 
     private Boolean isNumeric(String s) {
-        return null;
+        Pattern pattern = Pattern.compile("^[1-9 ]+$");
+        Matcher match = pattern.matcher(s);
+        return match.find();
     }
 }

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

@@ -1,6 +1,8 @@
 package rocks.zipcode;
 
 import java.io.IOException;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * @author leon on 18/11/2018.
@@ -12,9 +14,17 @@ public class SpecialCharDocument extends Document {
 
     @Override
     public void write(String contentToBeWritten) {
+        if(isSpecialCharacters(contentToBeWritten)) {
+            super.write(contentToBeWritten);
+        } else {
+            throw new IllegalArgumentException();
+        }
     }
 
     private Boolean isSpecialCharacters(String s) {
-        return null;
+
+        Pattern pattern = Pattern.compile("^[!@#$%^&*()_ ]+$");
+        Matcher match = pattern.matcher(s);
+        return match.find();
     }
 }