MAC:Fri Mar 25:08:12:B> jshell
|  Welcome to JShell -- Version 17.0.1
|  For an introduction type: /help intro

jshell> String s = "abcdefghij";
s ==> "abcdefghij"

jshell> s.charAt(0)
$2 ==> 'a'

jshell> s.substring(4)
$3 ==> "efghij"

jshell> s.substring(4,6)
$4 ==> "ef"

jshell> s.substring(0,4)
$5 ==> "abcd"

jshell> s.contains(fgh)
|  Error:
|  cannot find symbol
|    symbol:   variable fgh
|  s.contains(fgh)
|             ^-^

jshell> s.contains("fgh")
$6 ==> true

jshell> Math.cos(0)
$7 ==> 1.0

jshell> Math.exp(.69)
$8 ==> 1.9937155332430823

jshell> Math.pow(3,4)
$9 ==> 81.0

jshell> Math.factorial(6)
|  Error:
|  cannot find symbol
|    symbol:   method factorial(int)
|  Math.factorial(6)
|  ^------------^

jshell>