/* SELECT left.K, left.V1, right.V2 FROM left JOIN right ON left.K = right.K; */ public <K extends Comparable<K>, V1, V2> List<Triple<K, V1, V2>> join(List<Pair<K, V1>> left, List<Pair<K, V2>> right) { return null; } private static class Pair<A, B> { private A first; private B second; Pair(A first, B second) { this.first = first; this.second = second; } } private static class Triple<A, B, C> { private A first; private B second; private C third; Triple(A first, B second, C third) { this.first = first; this.second = second; this.third = third; } }