clarify

learnclj.clj

@@ -263,27 +263,41 @@ nil          ; => nil (Null/Nothing)
 
 ;; --- 14. Java Interop ---
 
-;; Method call
+;; === Method Calls ===
+
+;; Direct form: (. object methodName args…)
 (.toUpperCase "hello")   ; => "HELLO"
 (.substring "hello" 1 3) ; => "el"
+
+;; Field form: (. object fieldName) — for getters (no args)
 (. "hello" length)       ; => 5
-(.length "hello")        ; => 5
 (.age alice)              ; => 30
+
+;; Dot-dot (..): chained field access + method call
 (.. alice email toUpperCase) ; => "ALICE@EXAMPLE.COM"
+;; Equivalent to: (. (. alice email) toUpperCase)
 
-;; Static method
-(System/getProperty "user.name")  ; => "ajet"
+;; === Static Methods ===
 
-;; Constructor
+;; (Class/fieldName) or (Class/staticMethod args…)
+(System/getProperty "user.name")  ; => "ajet" (static field/property)
+(System/getProperty "java.version") ; => "21.0.x" (static method call)
+
+;; === Constructors ===
+
+;; (Class.) or (Class. arg1 arg2…)
 (java.util.Date.)  ; => #inst "2026-09-14T..." (current date/time)
+(java.util.Date. 2024 0 1) ; => #inst "2024-01-01T..."
 
 ;; --- 15. Threading Macros ---
 
 ;; Thread-first (->) — passes result as first arg
+;; Note: (.method args) inside -> is a method call on the threaded value
 (-> "hello"
-    (.toUpperCase)
-    (.replace "H" "J")
-    (.toLowerCase))  ; => "jello"
+    (.toUpperCase)              ; method call: .toUpperCase on "hello"
+    (.replace "H" "J")         ; method call: .replace on "HELLO"
+    (.toLowerCase))             ; method call: .toLowerCase on "JELLO"
+  ; => "jello"
 
 ;; Thread-last (->>) — passes result as last arg
 (->> [1 2 3 4 5]
@@ -297,7 +311,7 @@ nil          ; => nil (Null/Nothing)
 (try
   (/ 1 0)
   (catch ArithmeticException e
-    (str "Math error: " (.getMessage e))))  ; => "Math error: Divide by zero"
+    (str "Math error: " (.getMessage e))))  ; method call: (.getMessage e) => "Math error: Divide by zero"
 
 ;; assert — throws AssertionError on failure
 (assert (= 2 (+ 1 1)))  ; => nil (assert returns nil on success)