import java.util.*;
import org.apache.commons.math3.util.Combinations;
public class CombinationExample {
public static void main(String[] args) {
char[] characters = {'a', 'b', 'c'};
int combinationSize = 2;
Combinations combinations = new Combinations(characters.length, combinationSize);
Iterator<int[]> iterator = combinations.iterator();
while (iterator.hasNext()) {
int[] combinationIndices = iterator.next();
for (int index : combinationIndices) {
System.out.print(characters[index]);
}
System.out.println();
}
}
}
ab
ac
bc
