[java-decompiler] common file comparison method extracted; test data updated

testData/bulk/pkg/Main.java

@@ -0,0 +1,11 @@
+package pkg;
+
+import pkg.res.Loader;
+
+public class Main {
+   public static void main(String[] args) {
+      Loader loader = new Loader();
+      String resource = loader.getResource();
+      System.out.println(resource);
+   }
+}