Types.java

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

public final class Types
{
    private Types() {}

    public static <A, B extends A> B checkType(A value, Class<B> target, String name)
    {
        checkNotNull(value, "%s is null", name);
        checkArgument(target.isInstance(value),
                "%s must be of type %s, not %s",
                target.getName(),
                value.getClass().getName());
        return target.cast(value);
    }
}