jshell> s = "aardvark"
|  Error:
|  cannot find symbol
|    symbol:   variable s
|  s = "aardvark"
|  ^

jshell> String s = "aardvark"
s ==> "aardvark"

jshell> String y = "aardwolf"
y ==> "aardwolf"

jshell> s.compareTo(y)
$3 ==> -1

jshell> y.compareto(s)
|  Error:
|  cannot find symbol
|    symbol:   method compareto(java.lang.String)
|  y.compareto(s)
|  ^---------^

jshell> y.compareTo(s)
$4 ==> 1

jshell> BigInteger a = new BigInteger("1234")
a ==> 1234

jshell> BigInteger b = new BigInteger("2345")
b ==> 2345

jshell> a.compareTo(b)
$7 ==> -1

jshell> b.compareTo(a)
$8 ==> 1

jshell> a.compareTo(a)
$9 ==> 0

jshell> Comparable x = new BigInteger("3455");
x ==> 3455

jshell> x.add(a)
|  Error:
|  cannot find symbol
|    symbol:   method add(java.math.BigInteger)
|  x.add(a)
|  ^---^

jshell> Comparable q = "dfsdfser"
q ==> "dfsdfser"

jshell> q.charAt(0)
|  Error:
|  cannot find symbol
|    symbol:   method charAt(int)
|  q.charAt(0)
|  ^------^

jshell>