This code helped me get this behaviour: With a list a,b,c, I should get compared ab, ac and bc, but any other pair would be excess / not needed.
import java.util.*;
import static java.lang.System.out;
// rl = rawList; lr = listReversed
ArrayList<String> rl = new ArrayList<String>();
ArrayList<String> lr = new ArrayList<String>();
rl.add("a");
rl.add("b");
rl.add("c");
rl.add("d");
rl.add("e");
rl.add("f");
lr.addAll(rl);
Collections.reverse(lr);
for (String itemA : rl) {
lr.remove(lr.size()-1);
for (String itemZ : lr) {
System.out.println(itemA + itemZ);
}
}
The loop goes as like in this picture: Triangular comparison visual example
or as this:
| f e d c b a
------------------------------
a | af ae ad ac ab ·
b | bf be bd bc ·
c | cf ce cd ·
d | df de ·
e | ef ·
f | ·
total comparisons is a triangular number (n * n-1)/2