public class MapBuilder { public static <K, V> HashMap<K, V> newHashMap() { return new HashMap<>(); } public static <K, V> Map<K, V> of() { return newHashMap(); } public static <K, V> Map<K, V> of(K k1, V v1) { Map<K, V> map = of(); map.put(k1, v1); return map; } public static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2) { Map<K, V> map = of(); map.put(k1, v1); map.put(k2, v2); return map; } public static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) { Map<K, V> map = of(); map.put(k1, v1); map.put(k2, v2); map.put(k3, v3); return map; } public static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) { Map<K, V> map = of(); map.put(k1, v1); map.put(k2, v2); map.put(k3, v3); map.put(k4, v4); return map; } public static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) { Map<K, V> map = of(); map.put(k1, v1); map.put(k2, v2); map.put(k3, v3); map.put(k4, v4); map.put(k5, v5); return map; } public static <K, V> Map<K, V> of( K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6) { Map<K, V> map = of(); map.put(k1, v1); map.put(k2, v2); map.put(k3, v3); map.put(k4, v4); map.put(k5, v5); map.put(k6, v6); return map; } public static <K, V> Map<K, V> of( K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6, K k7, V v7) { Map<K, V> map = of(); map.put(k1, v1); map.put(k2, v2); map.put(k3, v3); map.put(k4, v4); map.put(k5, v5); map.put(k6, v6); map.put(k7, v7); return map; } public static <K, V> Builder<K, V> builder() { return new Builder<>(); } public static final class Builder<K, V> { private Map<K, V> map; private boolean underConstruction; private Builder() { map = newHashMap(); underConstruction = true; } public Builder<K, V> put(K k, V v) { if (!underConstruction) { throw new IllegalStateException("Underlying map has already been built"); } map.put(k, v); return this; } public Map<K, V> build() { if (!underConstruction) { throw new IllegalStateException("Underlying map has already been built"); } underConstruction = false; return map; } }}