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fbenedetti
2,010 PointsDo we need to check for non-letters? (TeacherAssistant.java)
Hi there!
I wonder if we'd check also for non-letters in this task. My second check was like this:
if (fieldName.charAt(1) != Character.toUpperCase(fieldName.charAt(1))){
throw new IllegalArgumentException("Second letter must be uppercase!");
}
I was puzzled to see that "m_first_name" still passed. Apparently, '_' is evaluated as uppercase:
java> String fieldName = "m_first_name"
java.lang.String fieldName = "m_first_name"
java> fieldName.charAt(1) != Character.toUpperCase(fieldName.charAt(1))
java.lang.Boolean res2 = false
java> Character.isLetter(fieldName.charAt(1))
java.lang.Boolean res1 = false
As '_' is not a letter, I had to add a third condition to the code in order to pass the test:
if (! Character.isLetter(fieldName.charAt(1))){
throw new IllegalArgumentException("Second letter must be a letter!");
}
if (fieldName.charAt(1) != Character.toUpperCase(fieldName.charAt(1))){
throw new IllegalArgumentException("Second letter must be uppercase!");
}
return fieldName;
Now, I wonder if that check is required or if there's a more elegant way to achieve the same result.
Cheers, F.
PS: I had a lot of enlightening troubles finding out that one cannot apply methods to primitives...
http://stackoverflow.com/questions/1418296/what-does-it-mean-to-say-a-type-is-boxed
My code that passed the task:
public class TeacherAssistant {
public static String validatedFieldName(String fieldName) {
// These things should be verified:
// 1. Member fields must start with an 'm'
if (fieldName.charAt(0) != 'm') {
throw new IllegalArgumentException("Field must start with an m character!");
}
// 2. The second letter in the field name must be uppercased to ensure camel-casing
// NOTE: To check if something is not equal use the != symbol. eg: 3 != 4
if (! Character.isLetter(fieldName.charAt(1))){
throw new IllegalArgumentException("Second letter must be a letter!");
}
if (fieldName.charAt(1) != Character.toUpperCase(fieldName.charAt(1))){
throw new IllegalArgumentException("Second letter must be uppercase!");
}
return fieldName;
}
}
3 Answers
Craig Dennis
Treehouse TeacherAlso....the reason why '_' is appearing to not be equal to Character.toUpperCase('_') is a little tricky. In Java the equality operator == is talking about if they represent the same object in memory. Much like Strings this is uber confusing at first...remember this:
"Weird" == new String("Weird") // This is false
"Weird".equals(new String("Weird")) // This is true
So chars behave similarly
'_' == Character.toUpperCase('_') // returns false
// The wrapper class exposes the equal method. chars by themselves don't have this capability
new Character('_').equals(Character.toUpperCase('_')) // returns true
We'll explore this more in an upcoming course.
Hope that helps!
fbenedetti
2,010 PointsThank you so much, Craig! I am looking forward to the next Java track! :)
Craig Dennis
Treehouse TeacherNice job! This is handy knowledge
Character.isUpperCase('_'); // returns false
Nice work digging around and sussing that out!