00_Example.java

Tuple2<String, Integer> x = new Tuple2<>("A", 10);
Tuple2<Integer, String> y = $(1, "B");

Map<Integer, String> xs = map($(1, "A"), $(2, "B"), $(3, "C"));

Collections.java

public class Collections {
     public static <K, V> java.util.Map<K, V> map(Tuple.Tuple2<K, V>... xs) {
        java.util.Map<K, V> map = new HashMap<>(xs.length);
        for (Tuple.Tuple2<K, V> x : xs) {
            map.put(x._1(), x._2());
        }
        return map;
    }
}

Tuple.java

public class Tuple {

    public static <T1, T2> Tuple2<T1, T2> $(T1 _1, T2 _2) {
        return new Tuple2<>(_1, _2);
    }

    public static class Tuple2<T1, T2> implements Serializable {

        public T1 _1;
        public T2 _2;

        public Tuple2(T1 _1, T2 _2) {
            this._1 = _1;
            this._2 = _2;
        }

        public T1 _1() {
            return _1;
        }

        public T2 _2() {
            return _2;
        }

        @Override
        public int hashCode() {
            int hash = 5;
            hash = 59 * hash + Objects.hashCode(this._1);
            hash = 59 * hash + Objects.hashCode(this._2);
            return hash;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj) {
                return true;
            }
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            final Tuple2<?, ?> other = (Tuple2<?, ?>) obj;
            if (!Objects.equals(this._1, other._1)) {
                return false;
            }
            if (!Objects.equals(this._2, other._2)) {
                return false;
            }
            return true;
        }

        @Override
        public String toString() {
            return "Tuple2{" + "_1=" + _1 + ", _2=" + _2 + '}';
        }

    }
}