Question

Is there a good reason why there is no Pair<L,R> in Java? What would be the equivalent of this C++ construct? I would rather avoid reimplementing my own.

It seems that 1.6 is providing something similar (AbstractMap.SimpleEntry<K,V>), but this looks quite convoluted.

Answer 1

In a thread on comp.lang.java.help, Hunter Gratzner gives some arguments against the presence of a Pair construct in Java. The main argument is that a class Pair doesn’t convey any semantics about the relationship between the two values (how do you know what ‘first’ and ‘second’ mean ?).

A better practice is to write a very simple class, like the one Mike proposed, for each application you would have made of the Pair class. Map.Entry is an example of a pair that carry its meaning in its name.

To sum up, in my opinion it is better to have a class Position(x,y), a class Range(begin,end) and a class Entry(key,value) rather than a generic Pair(first,second) that doesn’t tell me anything about what it’s supposed to do.