@Override
  public String getToolVersion() {
    return jibPluginDescriptor.getVersion();
  }
Gets the major version number from a Java version string.

<p>Examples: {@code "1.7" -> 7, "1.8.0_161" -> 8, "10" -> 10, "11.0.1" -> 11}

@param versionString the string to convert
@return the major version number as an integer, or 0 if the string is invalid
jib-maven-plugin/src/main/java/com/google/cloud/tools/jib/maven/MavenProjectProperties.java