Pipeline dosn't create artifacts

GitLab CI/CD
1

Hello,
i try to learn to use the Pipeline-System but ir ran into a problem. My pipeline finishes succesfully (als stages get a green checkmark) but in my outputfolder is no artifact (jar).

Here is my ci.yml (yes, the folder ’ artifacts/ ’ exists):

image: java:latest

stages:
- prepare
- build
- test
- pack
- cleanup

prepare:
stage: prepare
script: mkdir classes/; touch classes/.gitkeep
artifacts:
paths:
- classes/.gitkeep

build:
stage: build
script: /usr/lib/jvm/java-8-openjdk-amd64/bin/javac -g:none -verbose -d classes/ src/<single_java_file>.java
artifacts:
paths:
- classes/<single_class_file>.class

test:
stage: test
script: echo “insert tests here”
artifacts:
paths:
- classes/<single_class_file>.class

pack:
stage: pack
script: /usr/lib/jvm/java-8-openjdk-amd64/bin/jar -cvf artifacts/<single_jar_file>.jar classes/<single_class_file>.class
artifacts:
paths:
- artifacts/<single_jar_file>.jar

cleanup:
stage: cleanup
script: rm -r classes/
artifacts:
paths:
- artifacts/<single_jar_file>.jar