add files for exercise template

Author: SteffenLm

.github/workflows/format.yml

@@ -0,0 +1,15 @@
+name: format and commit all java files
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - 'exercises/**'
+      - 'solutions/**'
+
+jobs:
+  formatting:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: axel-op/googlejavaformat-action@v3

.gitignore

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+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*

Exercise.java

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+public class Exercise {
+
+  public static void main(String[] args) {
+    // implement exercise here
+  }
+}