Extending String class

Question

My job sucks. I need a Rope. Since I cannot extend final String (which I shouldn't anyway) I'm (thankfully) forced to create an aggregation of them. Or should I extend the new StringBuilder to make it create something stronger than an ordinairy String?
Today's just one of these days...

Answer 1

Because if you override equals and not hashCode you
violate the general contract for Object.hashCode and
your class will not function properly in conjunction
with all hash-based collections.
purpose of hashcode() I quote
"Since computing an object's equality is a time-consuming task, Java also provides a quick way of determining if an object is equal or not, using hashCode(). This returns a small number based on the object's internal datastructure; if two objects have different hash codes, then they cannot be equal to each other. (Think of it like searching for two words in a dictionary; if they both begin with "A" then they may be equal; however, if one begins with "A" and the other begins with "B" then they cannot be equal.)
The purpose of computing a hash code is that the hash should be quicker to calculate and compare than computing full object equality. Datastructures such as the HashMap implicitly use the hash code to avoid computing equality of objects where possible. One of the reasons why a HashMap looks up data faster than a List is because the list has to search the entire datastructure for a match, whereas the HashMap only searches those that have the same hash value.
Importantly, it is an error for a class to have an equals() method without overriding the default hashCode() method. In an inheritance hierarchy, only the top class needs to provide a hashCode() method. This is discussed further below. "