Update

src/zcl_demo_abap_constructor_expr.clas.locals_imp.abap

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+CLASS local_class DEFINITION.
+  PUBLIC SECTION.
+    METHODS: constructor IMPORTING txt TYPE string,
+      double IMPORTING int TYPE
+          REF TO i RETURNING VALUE(res) TYPE i.
+
+    DATA: timestamp TYPE string,
+          text      TYPE string.
+
+    CLASS-DATA: no_of_instances TYPE i READ-ONLY.
+ENDCLASS.
+
+CLASS local_class IMPLEMENTATION.
+  METHOD constructor.
+    "Number of instances of the class are counted.
+    no_of_instances = no_of_instances + 1.
+    "Set a time stamp.
+    DATA: ts TYPE timestampl.
+    GET TIME STAMP FIELD ts.
+    timestamp = |{ ts TIMESTAMP = SPACE }|.
+
+    text = |{ txt }, { sy-uname }.|.
+  ENDMETHOD.
+  METHOD double.
+    res = int->* * 2.
+  ENDMETHOD.
+ENDCLASS.