NumberFormatException when attempting to parse string as an integer

问题

Exception in thread "main" java.lang.NumberFormatException: For input string: " 400"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.lang.Integer.parseInt(Integer.java:470)
        at java.lang.Integer.parseInt(Integer.java:514)
        at Library.loadBooks(Library.java:191)
        at UseLibrary.main(UseLibrary.java:102)

what's the problem?

回答1:

You have a whitespace in " 400" that is resulting in a NumberFormatException.

Just use String.trim() before trying to parse.

Read the documentation for more information on String.trim().

回答2:

Use .trim() function to eliminate spaces.

Integer.valueOf(" 400".trim());

That function would avoid you this kind of problems.

来源：https://stackoverflow.com/questions/11085144/numberformatexception-when-attempting-to-parse-string-as-an-integer