The following snippet is in bigtop-packages/src/common/bigtop-utils/bigtop-detect-javahome:
# Uncomment and set the following variable in order for the
# guesswork step to be skipped
In a packaged world, however, bigtop-detect-javahome will be overridden with every subsequent release of bigtop. Defaults and configurations like this might go into /etc/default/bigtop or perhaps /etc/bigtop/..., so that users can configure permanently to enable or disable JAVA_HOME detection.