presto-main/src/main/java/io/prestosql/spiller/AesSpillCipher.java/AesSpillCipher/close
class AesSpillCipher:    @Override
    public void close()
    {
        /*
         * Setting the {@link AesSpillCipher#key} to null allows the key to be reclaimed by GC at the time of
         * destruction, even if the {@link AesSpillCipher} itself is still reachable for longer. When the key
         * is null, subsequent encrypt / decrypt operations will fail and can prevent accidental use beyond the
         * intended lifespan of the {@link AesSpillCipher}.
         */
        this.key = null;
        this.encryptSizer = null;
    }