The binary search tree requires that the keys be ordered. The basic types (int, double, char, ...) have a natural ordering and we use the relational operators <, >, etc.

Class types used as keys must implement the compareTo method, such as String.

So the binary search tree implementations of symbol table (and set) should implement the additional methods for ordered symbol tables:

• min
• max
• floor
• ceiling
• rank
• select

Implementing min and max is easy with the usual approach. What about the others?