Final answer:
Two String objects may not be equal under the == operator because == checks for reference equality, not content equality. The equals method should be used for comparing the content of strings.
Step-by-step explanation:
It is possible for two String objects with identical values not to be equal under the == operator in many programming languages, such as Java, because the == operator checks for reference equality, not content equality. When you use the == operator, you are asking whether two references point to the exact same object in memory, not whether the objects they point to are equivalent in terms of their content. If two String objects are created using the new operator, they will reside at different memory addresses, and hence, the == operator will return false even if the strings contain the exact same sequence of characters.
To properly compare the content of two strings, one must use the equals method, which is designed to compare the values inside the objects. If s1.equals(s2) returns true, it means that the content of the two strings is identical, even though they might be different objects in memory.