finished read and write in document class

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

@@ -1,21 +1,34 @@
 package rocks.zipcode;
 
+import java.io.BufferedWriter;
+import java.io.FileWriter;
 import java.io.IOException;
 
 /**
  * @author leon on 16/11/2018.
  */
 public class AlphaCharDocument extends Document {
+    Document document;
+
     public AlphaCharDocument(String fileName) throws IOException {
+
         super(fileName);
+
     }
 
     @Override
-    public void write(String contentToBeWritten) {
+    public void write(String contentToBeWritten) throws IOException {
+
+     
+
     }
 
     private Boolean isAlpha(String s) {
 
-        return null;
+        boolean allLetters = s.chars().allMatch(Character::isLetter);
+        return allLetters;
+
     }
+
+
 }

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

@@ -1,9 +1,14 @@
 package rocks.zipcode;
 
 import java.io.*;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.Arrays;
 import java.util.List;
+import java.util.stream.Stream;
 
 /**
  * @author leon on 16/11/2018.
@@ -13,6 +18,8 @@ public class Document implements DocumentInterface {
     private final FileWriter fileWriter;
     private final File file;
 
+
+
     public Document(String fileName) throws IOException {
         this(new File(fileName));
     }
@@ -22,17 +29,35 @@ public class Document implements DocumentInterface {
         this.fileWriter = new FileWriter(file);
     }
 
+
     @Override
-    public void write(String contentToBeWritten) {
+    public void write(String contentToBeWritten) throws IOException{
+        BufferedWriter writer = new BufferedWriter(new FileWriter(file));
+        writer.write(contentToBeWritten);
+        writer.close();
     }
 
     @Override
-    public void write(Integer lineNumber, String valueToBeWritten) {
+    public void write(Integer lineNumber, String valueToBeWritten) throws IOException {
+            List <String> lines = null;
+            try {
+                lines = Files.readAllLines(file.toPath());
+                lines.set(lineNumber,valueToBeWritten);
+                Files.write(file.toPath(), lines);
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+
     }
 
     @Override
-    public String read(Integer lineNumber) {
-        return null;
+    public String read(Integer lineNumber) throws IOException {
+
+        try(Stream<String> lines = Files.lines(Paths.get("target/file.txt"))){
+            String line = lines.skip(lineNumber).findFirst().get();
+            return line;
+        }
+
     }
 
     @Override
@@ -51,6 +76,21 @@ public class Document implements DocumentInterface {
 
     @Override
     public void replaceAll(String stringToReplace, String replacementString) {
+        Path path = Paths.get("target/file.txt");
+        Charset charset = StandardCharsets.UTF_8;
+
+        String content = null;
+        try {
+            content = new String(Files.readAllBytes(path), charset);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        content = content.replaceAll(stringToReplace, replacementString);
+        try {
+            Files.write(path, content.getBytes(charset));
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
     }
 
     @Override

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

@@ -1,17 +1,18 @@
 package rocks.zipcode;
 
 import java.io.File;
+import java.io.IOException;
 import java.util.List;
 
 /**
  * @author leon on 16/11/2018.
  */
 public interface DocumentInterface {
-    void write(String contentToBeWritten);
+    void write(String contentToBeWritten) throws IOException;
 
-    void write(Integer lineNumber, String valueToBeWritten);
+    void write(Integer lineNumber, String valueToBeWritten) throws IOException;
 
-    String read(Integer lineNumber);
+    String read(Integer lineNumber) throws IOException;
 
     String read();