I keep getting number format expectations, even though I\'m trimming the strings and they don\'t contain non numerical characters bizarrely it works for some numbers and not
It's because 3020857508 exceeds Integer.MAX_VALUE. You should use long to convert the string to number.
java> String n="3020857508";
//=> java.lang.String n = "3020857508"
java> Integer a = Integer.parseInt(n.trim());
//=> java.lang.NumberFormatException: For input string: "3020857508"
java> Integer.MAX_VALUE
//=> java.lang.Integer res2 = 2147483647
java> Long a = Long.parseLong(n.trim());
//=>java.lang.Long a = 3020857508
The above is javarepl output.
If you are using JDK9 or above, you can see the same result in jshell.
jshell> String n="3020857508"
n ==> "3020857508"
jshell> Integer a = Integer.parseInt(n.trim())
| Exception java.lang.NumberFormatException: For input string: "3020857508"
| at NumberFormatException.forInputString (NumberFormatException.java:65)
| at Integer.parseInt (Integer.java:652)
| at Integer.parseInt (Integer.java:770)
| at (#2:1)
jshell> Integer.MAX_VALUE
$3 ==> 2147483647
jshell> Long a = Long.parseLong(n.trim());
a ==> 3020857508