1 obj1.valueOf

     2 obj1 is 1

     3 obj1.valueOf

     4 11

     5 obj2.valueOf

     6 obj2 is 2

     7 obj2.valueOf

     8 24

     9 obj1.valueOf

    10 obj2.valueOf

    11 3

    12 obj3.toString

    13 world12

    14 obj3.toString

    15 hello world

    16 obj1.valueOf

    17 obj3.toString

    18 1world

    19 obj2.valueOf

    20 obj3.toString

    21 2world

    22 obj3.toString

    23 obj3.toString

    24 worldworld