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Daniel Kilders
36,793 PointsHow to express operator relevance or how to parse a string expression into an int
Hi! I have not been able to figure this out, so lets see if someone can help me :)
Developing in android studio i've noticed that that I can declare:
int number = ((5-8)*5)/2 ;
and log the comment with no problem. It will output the result of the expression. However, if I want to calculate the same based on user input from 1 edittext, I will get into issues.
How can I parse a string into an int without getting a NumberFormatException and it maintains operator relevance ?
2 Answers
Ben Deitch
Treehouse TeacherYou're looking for Integer.parseInt() :)
Daniel Kilders
36,793 PointsHmm... What I'm trying to build is a calculator that allows users to input expressions like " (1+5*(4-2)) " and that shows the result when clicked on the equal button.
What would you recommend me to look into in order to code it in the a proper way ?
Thanks for your help till now :)
Ben Deitch
Treehouse TeacherI'm not entirely sure what the best way would be, but I was able to find a worked calculator example that looks useful.
Daniel Kilders
36,793 PointsDaniel Kilders
36,793 PointsHi Ben !
if I use :
Integer.parseInt(myEditText.getText().toString());EditText content is based on user input. But something as simple as 5+6 will throw a NumberFormatException. Am I right?
EDIT: I'm parsing the whole expression from the same EditText and at the same time!
Ben Deitch
Treehouse TeacherBen Deitch
Treehouse TeacherOh now I see what you mean by 'operator relevance'. Yep, that's correct; the String "5+6" cannot be converted to a number. What you're really looking for then is a way to run Java code that's represented as a String and then retrieve the result of that code. This is a fairly difficult thing to do and I wouldn't recommend it, but I think it can be done by using something like Runtime.exec().