!= not working for string

jeffmarc

OK this is weird.

i have a string 12345.xxx

println(string.substring(string.length() - 3); // prints xxx to console

next line is:

if (string.substring(string.length() - 3) != "xxx")  {
  println(string + "yyy");
}

this is what prints to console:

12345.xxxyyy

It seems the if does not recognize the comparison!

I can't figure out why

GoToLoop

1. https://Processing.org/reference/String_equals_.html
2. https://Processing.org/reference/logicalNOT.html

String string = "12345.xxx";
String subStr = string.substring(string.length() - 3);
println(string, subStr);


if ( !"xxx".equals(subStr) )  println("Not equal to xxx!");
else                          println("Equal to xxx!");

exit();

jeffmarc

So is it necessary to create the subStr for the expression in the if to evaluate correctly? Why doesn't this work as well? Just want to understand for future if conditions about how functions are evaluated within if while switch etc.

if ( !"xxx".equals(string.substring(string.length()-3)

GoToLoop

So is it necessary to create the subStr...

No! I've declared variable subStr merely for aesthetic reasons, so the if () expression isn't too big and more clear. :-j

Reference for String::equals() method at https://processing.org/reference/String_equals_.html already explains why we should avoid using equality operators for comparing String objects under Java. L-)

jeremydouglass

Compares two strings to see if they are the same. This method is necessary because it's not possible to compare strings using the equality operator (==). Returns true if the strings are the same and false if they are not. https://processing.org/reference/String_equals_.html

For discussion see:

• https://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java