backup progress

src/main/java/rocks/zipcode/AlphaCharDocument.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 +14,17 @@ public class AlphaCharDocument extends Document {
 
     @Override
     public void write(String contentToBeWritten) {
+        if(isAlpha(contentToBeWritten)) {
+            super.write(contentToBeWritten);
+        } else {
+            throw new IllegalArgumentException();
+        }
     }
 
     private Boolean isAlpha(String s) {
-        return null;
+
+        Pattern pattern = Pattern.compile("^[a-zA-Z ]+$");
+        Matcher match = pattern.matcher(s);
+        return match.find();
     }
 }

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

@@ -1,8 +1,6 @@
 package rocks.zipcode;
 
 import java.io.*;
-import java.nio.file.Files;
-import java.util.Arrays;
 import java.util.List;
 
 /**
@@ -24,6 +22,15 @@ public class Document implements DocumentInterface {
 
     @Override
     public void write(String contentToBeWritten) {
+
+        BufferedWriter bw = null;
+        try {
+            bw = new BufferedWriter(new FileWriter(file));
+            bw.write(contentToBeWritten);
+            bw.close();
+        } catch (IOException e) {
+            System.out.println("Error writing to file");
+        }
     }
 
     @Override
@@ -32,12 +39,58 @@ public class Document implements DocumentInterface {
 
     @Override
     public String read(Integer lineNumber) {
-        return null;
+
+        BufferedReader reader = null;
+        String line = null;
+
+        try {
+            reader = new BufferedReader(new FileReader(file));
+            for (int i = 0; i <= lineNumber; i++) {
+
+                line = reader.readLine();
+            }
+
+        } catch (FileNotFoundException e) {
+            System.out.println("File not found");
+        } catch (IOException ioExep) {
+            ioExep.printStackTrace();
+        } finally {
+            try {
+                reader.close();
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+        return line;
     }
 
     @Override
     public String read() {
-        return null;
+
+        BufferedReader reader = null;
+        String line = null;
+        StringBuilder stringBuilder = new StringBuilder();
+        String ls = System.getProperty("line.separator");
+
+        try {
+            reader = new BufferedReader(new FileReader(file));
+            while ((line = reader.readLine()) != null) {
+                stringBuilder.append(line);
+                stringBuilder.append(ls);
+            }
+
+        } catch (FileNotFoundException e) {
+            System.out.println("File not found");
+        } catch (IOException ioExep) {
+            ioExep.printStackTrace();
+        } finally {
+            try {
+                reader.close();
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+        return stringBuilder.toString().trim();
     }
 
     @Override