fix(guide): simplify directory structure

guide/english/java/built-in-functions/index.md

@@ -0,0 +1,13 @@
+---
+title: Built-In Functions
+---
+# Built-In Functions
+
+Java also has many built-in or pre-defined functions which are usually stored in the java.lang and java.io packages,
+which are automatically imported in editors like BlueJ or can be imported using the following Syntax-
+```java
+import java.lang.*;
+import java.io.*;
+```
+
+These comprise functions which make an otherwise long and hard task easier to do.