Groovy enhances the File class with several methods. One is the deleteDir() method. With this method we can delete a directory with all it's subdirectories and files. So the directory doesn't need to be empty to run this method.
def mainDir = new File('test')
def subDir = new File(mainDir, 'app')
def file = new File(subDir, 'test.txt')
subDir.mkdirs() // Create directories.
file << 'sample' // Create file and add contents.
assert mainDir.exists() && subDir.exists() && file.exists()
def result = mainDir.deleteDir() // Returns true if all goes well, false otherwise.
assert result
assert !mainDir.exists() && !subDir.exists() && !file.exists()
