code: public boolean isInstalled()
        throws ManagedSdkVerificationException, ManagedSdkVersionMismatchException {
      if (getSdkHome() == null) {
        return false;
      }
      if (!Files.isDirectory(getSdkHome())) {
        return false;
      }
      if (!Files.isRegularFile(getGcloudPath())) {
        return false;
      }
      // Verify the versions match up for fixed version installs
      if (version != Version.LATEST) {
        try {
          String versionFileContents =
              new String(Files.readAllBytes(getSdkHome().resolve("VERSION")), StandardCharsets.UTF_8)
                  .trim();
          if (!versionFileContents.equals(version.getVersion())) {
            throw new ManagedSdkVersionMismatchException(
                "Installed sdk version: "
                    + versionFileContents
                    + " does not match expected version: "
                    + version.getVersion()
                    + ".");
          }
        } catch (IOException ex) {
          throw new ManagedSdkVerificationException(ex);
        }
      }
      return true;
    }
docs: Simple check to verify Cloud SDK installed by verifying the existence of gcloud.