Resolve build errors & cleanup structure (#2334)

.github/workflows/build.yml

@@ -1,20 +1,14 @@
-name: Build Project
-
-on:
-  pull_request:
-  push:
-    branches:
-    - master
-
+name: Build
+on: push
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
-      - name: Set up JDK 12
+      - name: Set up JDK 17
         uses: actions/setup-java@v1
         with:
-          java-version: 12
+          java-version: 17
       - run: find . -type f -name "*.java" > sources.txt
       - run: javac @sources.txt