我需要把所有的字符串组合在一个数组的所有集合中 Map<String, Set<String>> 唯一字符串的组合。集合的数量可以变化，集合中的字符串数量也可以变化。
我脑子里想不起来。示例代码为：

// Create a map
Map<String, Set<String>> map = new HashMap<String, Set<String>>();
// Create setA
Set<String> setA = new HashSet<String>();
setA.add("A");
setA.add("B");
// There could be more (or less) values in setA
// Create setB
Set<String> setB = new HashSet<String>();
setB.add("X");
setB.add("Y");
// There could be more (or less) values in setB
// Create setC
Set<String> setC = new HashSet<String>();
setC.add("1");
setC.add("2");
// There could be more (or less) values in setC
// Add sets to map
map.put("a", setA);
map.put("b", setB);
map.put("c", setC);
// There could be more sets to add to the map

/*
 * Combine each value from each set in the
 * map {a=[A, B], b=[X, Y], c=[1, 2]} to
 * unique strings. Output should be:
 * A X 1
 * A X 2
 * A Y 1
 * A Y 2
 * B X 1
 * B X 2
 * B Y 1
 * B Y 2
 * ... more combinations if there are more values
 */