Start creating FileSystem class

src/main/java/ru/redguy/tftpserver/IDataSource.java

@@ -0,0 +1,5 @@
+package ru.redguy.tftpserver;
+
+public interface IDataSource {
+    public boolean isFileExists(String localPath);
+}

src/main/java/ru/redguy/tftpserver/datasource/FileSystem.java

@@ -0,0 +1,31 @@
+package ru.redguy.tftpserver.datasource;
+
+import ru.redguy.tftpserver.IDataSource;
+
+import java.io.File;
+import java.nio.file.Path;
+
+public class FileSystem implements IDataSource {
+
+    String path;
+
+    public FileSystem(File file) {
+        path = file.getAbsolutePath()+"/";
+    }
+
+    public FileSystem(Path path) {
+        this.path = path.toAbsolutePath().toString()+"/";
+    }
+
+    public FileSystem(String path) {
+        this.path = path;
+        if(!this.path.endsWith("/")) {
+            this.path = this.path+"/";
+        }
+    }
+
+    @Override
+    public boolean isFileExists(String localPath) {
+        return new File(this.path,localPath).exists();
+    }
+}