class Pair<K, V> {
    private final K key;
    private final V value;

    public Pair(K key, V value) {
        this.key = key;
        this.value = value;
    }

    public K getKey() {
        return key;
    }

    public V getValue() {
        return value;
    }

    @Override
    public String toString() {
        return "(" + key + ", " + value + ")";
    }
}

class PairUtil {
    public static <K, V> Pair<V, K> swapPair(Pair<K, V> pair) {
        return new Pair<>(pair.getValue(), pair.getKey());
    }
}

public class Main {
    public static void main(String[] args) {
        Pair<String, Integer> p1 = new Pair<>("age", 20);
        System.out.println("原始 p1: " + p1);
        Pair<Integer, String> swappedP1 = PairUtil.swapPair(p1);
        System.out.println("交换后 p1: " + swappedP1);

        Pair<Integer, Double> p2 = new Pair<>(100, 99.5);
        System.out.println("\n原始 p2: " + p2);
        Pair<Double, Integer> swappedP2 = PairUtil.swapPair(p2);
        System.out.println("交换后 p2: " + swappedP2);

        Pair<String, String> p3 = new Pair<>("key", "value");
        System.out.println("\n原始 p3: " + p3);
        Pair<String, String> swappedP3 = PairUtil.swapPair(p3);
        System.out.println("交换后 p3: " + swappedP3);
    }
}