fix(scala): Java 8/11/17/21 互換性対応

.github/workflows/test-scala.yml

@@ -18,7 +18,10 @@ permissions:
 jobs:
   build:
     runs-on: ubuntu-latest
-    name: Build
+    name: Build (Java ${{ matrix.java-version }})
+    strategy:
+      matrix:
+        java-version: ['8', '11', '17', '21']
     timeout-minutes: 5
     defaults:
       run:
@@ -32,7 +35,7 @@ jobs:
       - uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5
         with:
           distribution: temurin
-          java-version: '21'
+          java-version: ${{ matrix.java-version }}
           cache: sbt
       - uses: sbt/setup-sbt@af116cce31c00823d3903ce687f9cda3a4f19f1b # v1
       - run: sbt compile

scala/README.md

@@ -2,8 +2,6 @@
 
 ## 開発
 
-NOTE: java21未満を利用する場合は `project/build.properties` を変更して sbt `1.11.7` などを利用してください
-
 ```shell
 # 準備
 git init && git add . && git commit -m init

scala/build.sbt

@@ -1,4 +1,4 @@
-val scala3Version = "3.8.3"
+val scala3Version = "3.3.5"
 
 lazy val root = project
   .in(file("."))

scala/project/build.properties

@@ -1 +1 @@
-sbt.version=1.12.9
+sbt.version=1.9.9