public static boolean isDefaultDockerInstalled() {
    try {
      new ProcessBuilder(DEFAULT_DOCKER_CLIENT.toString()).start();
      return true;
    } catch (IOException ex) {
      return false;
    }
  }
Checks if Docker is installed on the user's system by running the `docker` command.

@return {@code true} if Docker is installed on the user's system and accessible
jib-core/src/main/java/com/google/cloud/tools/jib/docker/CliDockerClient.java