I wonder is some of this can be cleared up by simply giving the java plugin a default task (likely "assemble") and making the error message more verbose in the case of either no build.gradle, or a build.gradle without a src directory. In some sense a new user types "gradle" and expects either something useful to happen, or at least a Usage that will point them in the correct direction. Currently you get a message about "No tasks", telling you to run gradle -t, which then says "No Tasks". Not terribly helpful someone new to gradle.

Perhaps in the case of no build.gradle you should get:

FAILURE: Unable to find 'build.gradle' in current directory.

• What went wrong:
  There is not a build.gradle file in the current directory and one was not specified on the command line.

• Try:
  Create a build.gradle file in the current directory. The simplest instance, for a java project is:

apply plugin: 'java'

See http://www.gradle.org/bla/bla/bla for more information on getting started with gradle.

And in the case of a build.gradle with apply plugin: 'java', but without a source directory, you currently get a successful build, with an empty jar file. Seems like the java plugin should make sure there is at least one source file, or maybe just a src/main/java before proceeding to the jar task. Maybe an error message like:

FAILURE: Could not find a source directory.

• What went wrong:
  No source directory, usually src/main/java, exists.

• Try:
  Create the src/main/java directory and place your java source files in it.

Even if there is a "make my directories" task, I think these changes would be helpful.