public class Pair { private final L left; private final R right; public Pair(L left, R right) { assert left != null; assert right != null; this.left = left; this.right = right; } public L getLeft() { return left; } public R getRight() { return right; } @Override public int hashCode() { return left.hashCode() ^ right.hashCode(); } @Override public boolean equals(Object o) { if (!(o instanceof Pair)) return false; Pair pairo = (Pair) o; return this.left.equals(pairo.getLeft()) && this.right.equals(pairo.getRight()); } }