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Java Java Objects Meet Objects Welcome Back

Dot notation to Check for Equality vs. Double Equals ( == )

Craig seems to switch suddenly to checking for equality using dot notation in the Welcome Back Objects video vs. the double equals (==). Why the sudden change? Is there an advantage to using one over the other to compare equality? Or are they both just a different way to accomplish the same task? Thanks!

3 Answers

Seth Kroger
Seth Kroger
56,413 Points

== works for comparing the values of primitive variables because they are essentially numbers. Object variables on the other hand are what's called "reference variables", it a reference to a point in memory where the object was created by the newkeyword. This distinction is usually handled transparently, but not here. == doesn't work for comparing the values of objects because the basic numeric value isn't based on what the content of the object is, but on what the location where the object is at in memory. Two objects with the same internal values wouldn't be considered equal by == because they reside in two different locations. This is why using (and defining in you own classes) .equals() is important with objects.

Excellent answer, thank you!

String is a type of object, hence why it is uppercase. Because String is an object, you use the method .equals to check for equality.

You are now learning about this in the objects course since it would have been too much in the java basics course.

int is not a method and is a primitive data type, so == is still valid to use.

Craig Dennis
STAFF
Craig Dennis
Treehouse Teacher

Hi nekilof ,

Strings need to be checked with the equals or equalsIgnoreCase method. I made a workshop on this that explains why, if you want to dig deeper: The Thing About Strings

Hope that helps!