build.gradle: require JDK 11 for the build

Uses javac -release option to validate API for older JDK.

.github/workflows/gradle.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macOS-latest, windows-latest]
-        java: ['8', '11', '17']
+        java: ['11', '17']
         distribution: ['temurin']
         gradle: ['7.3.2']
         include:

README.md

@@ -22,13 +22,13 @@ To get started, it is best to have the latest JDK and Gradle installed. The HEAD
 
 #### Building from the command line
 
-Official builds are currently using with JDK 8, even though the `core` module is compatible with JDK 7 and later.
+Official builds are currently using JDK 11. Our GitHub Actions build and test with JDK 11 and JDK 17.
 
-To perform a full build (*including* JavaDocs and unit/integration *tests*) use JDK 8+
+To perform a full build (*including* JavaDocs and unit/integration *tests*) use JDK 11+.
 ```
 gradle clean build
 ```
-If you are running JDK 11 or later and Gradle 4.10 or later, the build will automatically include the JavaFX-based `wallettemplate` module. The outputs are under the `build` directory.
+If you are using Gradle 4.10 or later, the build will automatically include the JavaFX-based `wallettemplate` module. The outputs are under the `build` directory.
 
 To perform a full build *without* unit/integration *tests* use:
 ```

core/build.gradle

@@ -1,3 +1,5 @@
+import org.gradle.util.GradleVersion
+
 plugins {
     id 'java-library'
     id 'com.google.protobuf'
@@ -25,12 +27,16 @@ dependencies {
     testImplementation 'org.hamcrest:hamcrest-library:2.2'
 }
 
-sourceCompatibility = 1.7
-targetCompatibility = 1.8
+sourceCompatibility = 8
+targetCompatibility = 8
 compileJava.options.encoding = 'UTF-8'
 compileTestJava.options.encoding = 'UTF-8'
 javadoc.options.encoding = 'UTF-8'
 
+compileJava {
+    options.compilerArgs.addAll(['--release', '8'])
+}
+
 protobuf {
     protoc {
         artifact = 'com.google.protobuf:protoc:3.18.0'

examples/build.gradle

@@ -10,7 +10,11 @@ dependencies {
     implementation 'org.fusesource.leveldbjni:leveldbjni-all:1.8'
 }
 
-sourceCompatibility = 1.8
+sourceCompatibility = 8
 compileJava.options.encoding = 'UTF-8'
 compileTestJava.options.encoding = 'UTF-8'
 javadoc.options.encoding = 'UTF-8'
+
+compileJava {
+    options.compilerArgs.addAll(['--release', '8'])
+}

settings.gradle

@@ -1,7 +1,7 @@
 import org.gradle.util.GradleVersion
 import org.gradle.api.GradleScriptException
 
-// Minimum Gradle version for main build
+// Minimum Gradle version for build
 def minGradleVersion = GradleVersion.version("4.4")
 // Minimum Gradle version for builds of JavaFX 11 module
 def minFxGradleVersion = GradleVersion.version("4.10")
@@ -12,6 +12,10 @@ if (GradleVersion.current().compareTo(minGradleVersion) < 0) {
     throw new GradleScriptException("bitcoinj build requires Gradle ${minGradleVersion} or later", null)
 }
 
+if (!JavaVersion.current().isJava11Compatible()) {
+    throw new GradleScriptException("bitcoinj build requires Java 11 or later", null)
+}
+
 include 'core'
 project(':core').name = 'bitcoinj-core'
 
@@ -21,10 +25,9 @@ project(':tools').name = 'bitcoinj-tools'
 include 'examples'
 project(':examples').name = 'bitcoinj-examples'
 
-if (GradleVersion.current().compareTo(minFxGradleVersion) >= 0 && JavaVersion.current().isJava11Compatible()) {
-    System.err.println "Including wallettemplate because ${GradleVersion.current()} and Java ${JavaVersion.current()}"
+if (GradleVersion.current().compareTo(minFxGradleVersion) > 0) {
+    System.err.println "Including wallettemplate because ${GradleVersion.current()}"
     include 'wallettemplate'
     project(':wallettemplate').name = 'bitcoinj-wallettemplate'
-} else {
-    System.err.println "Skipping wallettemplate, requires ${minFxGradleVersion}+ and Java 11+, currently running: ${GradleVersion.current()} and Java ${JavaVersion.current()}"
 }
+

tools/build.gradle

@@ -10,11 +10,15 @@ dependencies {
     implementation 'org.slf4j:slf4j-jdk14:1.7.32'
 }
 
-sourceCompatibility = 1.8
+sourceCompatibility = 8
 compileJava.options.encoding = 'UTF-8'
 compileTestJava.options.encoding = 'UTF-8'
 javadoc.options.encoding = 'UTF-8'
 
+compileJava {
+    options.compilerArgs.addAll(['--release', '8'])
+}
+
 mainClassName = "org.bitcoinj.tools.WalletTool"
 applicationName = "wallet-tool"
 

wallettemplate/build.gradle

@@ -17,9 +17,13 @@ javafx {
     modules = [ 'javafx.controls', 'javafx.fxml' ]
 }
 
-sourceCompatibility = 1.11
+sourceCompatibility = 11
 compileJava.options.encoding = 'UTF-8'
 compileTestJava.options.encoding = 'UTF-8'
 javadoc.options.encoding = 'UTF-8'
 
+compileJava {
+    options.compilerArgs.addAll(['--release', '11'])
+}
+
 mainClassName = 'wallettemplate.Main'