reconfigure build: target jdk -release=8 (#368)

* -release 8 for both javac and scalac
* build with jdk19
* document in readme

Author: mpollmeier

.github/workflows/pr.yml

@@ -7,11 +7,11 @@ jobs:
       - uses: actions/checkout@v2
         with:
           fetch-depth: 1
-      - name: Set up JDK 11
-        uses: actions/setup-java@v2
+      - name: Set up JDK
+        uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: 11
+          java-version: 19
       - uses: actions/cache@v2
         with:
           path: |

.github/workflows/release.yml

@@ -19,11 +19,11 @@ jobs:
         run: echo $PGP_SECRET | base64 --decode | gpg --batch --import
         env:
           PGP_SECRET: ${{ secrets.PGP_SECRET }}
-      - name: Set up JDK 11
-        uses: actions/setup-java@v2
+      - name: Set up JDK
+        uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
-          java-version: 11
+          java-version: 19
       - uses: actions/cache@v2
         with:
           path: |

README.md

@@ -144,6 +144,10 @@ never hold a (strong) reference onto them in your main application: it would inh
 `overflowdb.util.DiffTool.compare(graph1, graph2)` allows you to do some very basic comparison of two graphs. It identifies nodes by their ids, and compares their existence, properties, adjacent edges and properties of those edges. 
 
 ### FAQ
+1. **What JDK does OverflowDB support?**
+The build targets JDK8, so that's the minimum version. However it is highly encouraged to use a modern JVM, such as JDK20. 
+The build itself requires JDK11+ though. 
+
 1. **Why not just use a simple cache instead of the overflow mechanism?**  
 Regular caches require you have to specify a fixed size. OverflowDB is designed to run in the same JVM as your main application, and since 
 most applications have varying memory needs over time, it would be hard/impossible to achieve our goal *use your entire heap and prevent OutOfMemoryError* 

build.sbt

@@ -18,18 +18,15 @@ ThisBuild/libraryDependencies ++= Seq(
   "org.scalatest" %% "scalatest" % "3.2.15" % Test,
 )
 
-ThisBuild/scalacOptions ++= Seq("-deprecation", "-feature") ++ (
-  CrossVersion.partialVersion(scalaVersion.value) match {
-    case Some((3, _)) =>
-      Seq("-Xtarget:8")
-    case _ =>
-      Seq("-target:jvm-1.8", "--release", "8")
-  }
+ThisBuild/scalacOptions ++= Seq(
+  "-release", "8",
+  "-deprecation",
+  "-feature"
 )
 
 ThisBuild / compile / javacOptions ++= Seq(
   "-g", //debug symbols
-  "--release=8"
+  "--release", "8"
 )
 
 ThisBuild/Test/testOptions += Tests.Argument(TestFrameworks.JUnit, "-a", "-v")