From http://stackoverflow.com/questions/29809105/how-do-i-delete-a-versioned-bucket-in-aws-s3-using-the-cli/29882352#29882352

delete_all_versions.java

AmazonS3Client s3 = new AmazonS3Client();
String bucketName = "deleteversions-"+UUID.randomUUID();

//Creates Bucket
s3.createBucket(bucketName);

//Enable Versioning
BucketVersioningConfiguration configuration = new BucketVersioningConfiguration(ENABLED);
s3.setBucketVersioningConfiguration(new SetBucketVersioningConfigurationRequest(bucketName, configuration ));

//Puts versions
s3.putObject(bucketName, "some-key",new ByteArrayInputStream("some-bytes".getBytes()), null);
s3.putObject(bucketName, "some-key",new ByteArrayInputStream("other-bytes".getBytes()), null);

//Removes all versions
for ( S3VersionSummary version : S3Versions.inBucket(s3, bucketName) ) {
    String key = version.getKey();
    String versionId = version.getVersionId();          
    s3.deleteVersion(bucketName, key, versionId);
}

//Removes the bucket
s3.deleteBucket(bucketName);
System.out.println("Done!");