Validated.java

Validated.java

public final class Validated<E, V> {
    private final E validationError;
    private final V value;

    private Validated(E e, V v) {
        this.validationError = e;
        this.value = v;
        checkState();
    }

    public static <E, V> Validated<E,V> valid(V v) {
        return new Validated<>(null, v);
    }

    public static <E, V> Validated<E,V> invalid(E e) {
        return new Validated<>(e, null);
    }

    public  boolean isValid() {
        return this.value!=null && this.validationError==null;
    }

    public boolean isInvalid() {
        return this.value==null && this.validationError!=null;
    }

    private void checkState() {
        if (isValid() == isInvalid()) {
            throw new IllegalArgumentException("ValidationError = " + this.validationError + ", value=" + this.value);
        }
    }
}