Generics.java

public class Main {
    public static void main(String[] args) {
        Pair<Double, Integer> pair = new Pair<>(100d, 100);
    }

    static class Pair<L extends Number, R> {
        private L left;
        private R right;

        public Pair(L left, R right) {
            this.left = left;
            this.right = right;
        }

        public L getLeft() {
            return left;
        }

        public R getRight() {
            return right;
        }
    }
}

int primitive
Integer object