private synchronized int newKeyId() {
    int keyId = Util.randKeyId();
    while (keyIdExists(keyId)) {
      keyId = Util.randKeyId();
    }
    return keyId;
  }
Destroys the key material associated with the {@code keyId}.

@throws GeneralSecurityException if the key is not found or it is the primary key
java_src/src/main/java/com/google/crypto/tink/KeysetManager.java