code: void setTempDir() {
          synchronized (AbstractDatabaseConfiguration.class) {
              final String tempDir = getTempDir();
              if (!tempDir.equals(AbstractDatabaseConfiguration.tempDir)) {
                  AbstractDatabaseConfiguration.tempDir = tempDir;
                  C4Base.setTempDir(AbstractDatabaseConfiguration.tempDir);
              }
          }
      }
docs: Set the temp directory based on Database Configuration.
  The default temp directory is APP_CACHE_DIR/Couchbase/tmp.
  If a custom database directory is set, the temp directory will be
  CUSTOM_DATABASE_DIR/Couchbase/tmp.