java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.substring(int, int) Fatal Exception main
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please add your code – Sami Kanafani Jun 28 '17 at 17:54
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@SamiKanafani this is not necessary, it is a duplicate anyhow. – Henry Jun 28 '17 at 17:56
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This exception is thrown when you are trying to use the substring method on a null string, try checking the value of the string you are invoking the substring method. If you want to avoid the crash you can use the following code
if(str!=null){
//where the str is the string you are invoking the method on
substr = str.substring(7, 17);
}
Sami Kanafani
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Since this is more often than not a programming error, the crash is preferable over some strange misbehaviour due to substr not being set. (Fail fast). – Henry Jun 28 '17 at 18:15