Manage license headers via spotless

For package-info.java and module-info.java files, the plain java group
does not work. Therefore, an additional "javaMisc" formatting group was
defined with the sole purpose of these files.

Author: damianmalczewski

build.gradle.kts

@@ -35,8 +35,11 @@ nmcp {
 }
 
 spotless {
+    val licenseHeader = "${rootProject.rootDir}/gradle/license-header.java"
+
     java {
         target("**/src/**/*.java")
+        licenseHeaderFile(licenseHeader).updateYearWithLatest(true)
 
         // NOTE: decided not to upgrade Google Java Format, as versions 1.29+ require running it on Java 21
         googleJavaFormat("1.28.0")
@@ -45,6 +48,15 @@ spotless {
         lineEndings = LineEnding.UNIX
     }
 
+    format("javaMisc") {
+        target("**/src/**/package-info.java", "**/src/**/module-info.java")
+
+        // License headers in these files are not formatted with standard java group, so we need to use custom settings.
+        // The regex is designed find out where the code starts in these files, so the license header can be placed
+        // before it. The code starts with either "package", "import", "module" or "/**" in case of a global JavaDoc.
+        licenseHeaderFile(licenseHeader, "^(package|import|module|/\\*\\*)").updateYearWithLatest(true)
+    }
+
     kotlin {
         target("**/src/**/*.kt")
 

gradle/license-header.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2025-$YEAR The Problem4J Authors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+

src/main/java/io/github/problem4j/core/AbstractProblem.java

@@ -18,6 +18,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
 package io.github.problem4j.core;
 
 import java.io.Serializable;

src/main/java/io/github/problem4j/core/AbstractProblemBuilder.java

@@ -18,6 +18,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
 package io.github.problem4j.core;
 
 import java.io.Serializable;

src/main/java/io/github/problem4j/core/AbstractProblemContext.java

@@ -18,6 +18,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
 package io.github.problem4j.core;
 
 import java.io.Serializable;

src/main/java/io/github/problem4j/core/AbstractProblemMapper.java

@@ -18,6 +18,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
 package io.github.problem4j.core;
 
 import java.lang.reflect.Field;

src/main/java/io/github/problem4j/core/Problem.java

@@ -18,6 +18,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
 package io.github.problem4j.core;
 
 import java.net.URI;

src/main/java/io/github/problem4j/core/ProblemBuilder.java

@@ -18,6 +18,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
 package io.github.problem4j.core;
 
 import java.net.URI;

src/main/java/io/github/problem4j/core/ProblemBuilderImpl.java

@@ -18,6 +18,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
 package io.github.problem4j.core;
 
 final class ProblemBuilderImpl extends AbstractProblemBuilder {

src/main/java/io/github/problem4j/core/ProblemContext.java

@@ -18,6 +18,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
+
 package io.github.problem4j.core;
 
 import java.util.Map;