Unexpected Boolean Result

Question

I have the following Java code:

String p = "seven";
String q = "teen";
p + q == "seventeen";

Why does the last line return false and not true?

Answer 1

Because you should use the equals method for String comparison. The == operator compares the object references, and those are unique for each object. You would only get true for a == comparison when comparing an object to itself.

Try (p + q).equals("seventeen");

Note, that Stringcomparison in java is case-sensitive, so you might also want to take a look at the equalsIgnoreCase method.

Answer 2

(p + q).intern() == "seventeen"

intern will return the string from the pool

Answer 3

When comparing Strings, you must use the String method equals or equalsIgnoreCase, otherwise you are comparing objects. since p + q is a different object than "seventeen", your result will be false.

Answer 4

Because == is reference equality and not logical equality. Strings are immutable so you are getting new Strings, which won't be the same location in memory. Try:

String p = "seven";
String q = "teen";
(p + q).equals("seventeen");