ICU-23368 Update JDK for tools to 21

.cpyskip.txt

@@ -110,7 +110,7 @@ icu4j/perf-tests/data/collation/ulyss10.txt
 icu4j/perf-tests/data/collation/2drvb10.txt
 icu4j/perf-tests/data/collation/vfear11a.txt
 icu4j/perf-tests/data/collation/nvsbl10.txt
-icu4j/tools/build/src/main/resources/com/ibm/icu/dev/tool/errorprone/sorttable.js
+icu4j/tools/errorprone_report/src/main/resources/com/ibm/icu/dev/tool/errorprone/sorttable.js
 #
 # docs
 #

.github/workflows/icu4j.yml

@@ -134,8 +134,8 @@ jobs:
             grep '^\[ERROR\] ' /tmp/errorprone.log
             # We need to build this sub-project. If maven fails in a previous sub-project the
             # whole build stops and we never get to build the report tool, so we can't run it.
-            mvn install -f icu4j/tools/build/ -q
-            mvn exec:java -f icu4j/tools/build/ -P errorprone_report -DlogFile=/tmp/errorprone.log
+            mvn install -f icu4j/tools/errorprone_report/ -q
+            mvn exec:java -f icu4j/tools/errorprone_report/ -DlogFile=/tmp/errorprone.log
             # Output messages and the error-prone report as workflow job summary
             echo '**Run this command locally and fix all errors:**' >> $GITHUB_STEP_SUMMARY
             echo '```' >> $GITHUB_STEP_SUMMARY

icu4j/main/core/src/test/java/com/ibm/icu/dev/test/UnicodeMapBoilerplateTest.java

@@ -11,14 +11,15 @@
 import com.ibm.icu.impl.UnicodeMap;
 import java.util.List;
 import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
 
 /** Moved from UnicodeMapTest */
+@RunWith(JUnit4.class)
 public class UnicodeMapBoilerplateTest extends TestBoilerplate<UnicodeMap<String>> {
 
     private static String[] TEST_VALUES = {"A", "B", "C", "D", "E", "F"};
 
-    public void TestUnicodeMapBoilerplate() throws Exception {}
-
     @Test
     public void test() throws Exception {
         _test();

icu4j/main/core/src/test/java/com/ibm/icu/dev/test/UnicodeSetBoilerplateTest.java

@@ -11,12 +11,13 @@
 import com.ibm.icu.text.UnicodeSet;
 import java.util.List;
 import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
 
 /** Moved from UnicodeMapTest */
+@RunWith(JUnit4.class)
 public class UnicodeSetBoilerplateTest extends TestBoilerplate<UnicodeSet> {
 
-    public void TestUnicodeSetBoilerplate() throws Exception {}
-
     @Test
     public void test() throws Exception {
         _test();

icu4j/tools/build/pom.xml

@@ -13,68 +13,11 @@
 
   <artifactId>tools_build</artifactId>
 
-  <properties>
-    <!-- Arguments for the errorprone report generation -->
-    <logFile>/tmp/errorprone.log</logFile>
-    <outDir>${project.build.directory}/errorprone_report</outDir>
-    <srcBaseUrl>https://github.com/unicode-org/icu/blob/main/</srcBaseUrl>
-  </properties>
-
   <dependencies>
-    <dependency>
-      <groupId>com.google.errorprone</groupId>
-      <artifactId>error_prone_core</artifactId>
-    </dependency>
     <dependency>
       <groupId>commons-cli</groupId>
       <artifactId>commons-cli</artifactId>
     </dependency>
   </dependencies>
 
-  <profiles>
-    <profile>
-      <!--
-      From icu4j:
-        mvn clean test -ntp -DskipTests -DskipITs -l /tmp/errorprone.log -P errorprone
-        mvn exec:java -f tools/build/ -P errorprone_report -DlogFile=/tmp/errorprone.log
-
-      The links to the source files go to the main GitHub repo (`main` branch).
-        But when we work locally, or in a fork / branch, the links might point to an incorrect file / line.
-        You can override the URL by passing -DsrcBaseUrl in the maven command line.
-        For local files it would be easy to do:
-          mvn exec:java -f tools/build/ -P errorprone_report  -DsrcBaseUrl=$PWD/..
-        Note: jumping to a certain line does not work on local files.
-          This is a limitation in how browsers work.
-          So opening the file in an IDE is probably more practical.
-      -->
-      <id>errorprone_report</id>
-      <build>
-        <plugins>
-          <plugin>
-            <groupId>org.codehaus.mojo</groupId>
-            <artifactId>exec-maven-plugin</artifactId>
-            <executions>
-              <execution>
-                <goals>
-                  <goal>java</goal>
-                </goals>
-              </execution>
-            </executions>
-            <configuration>
-              <mainClass>com.ibm.icu.dev.tool.errorprone.Main</mainClass>
-              <arguments>
-                <argument>--logFile</argument>
-                <argument>${logFile}</argument>
-                <argument>--srcBaseUrl</argument>
-                <argument>${srcBaseUrl}</argument>
-                <argument>--outDir</argument>
-                <argument>${outDir}</argument>
-              </arguments>
-            </configuration>
-          </plugin>
-        </plugins>
-      </build>
-    </profile>
-  </profiles>
-
 </project>

icu4j/tools/errorprone_report/pom.xml

@@ -0,0 +1,80 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+* © 2023 and later: Unicode, Inc. and others.
+* License & terms of use: http://www.unicode.org/copyright.html
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.ibm.icu</groupId>
+    <artifactId>icu4j-tools</artifactId>
+    <version>79.0.1-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>errorprone_report</artifactId>
+
+  <properties>
+    <!-- Arguments for the errorprone report generation -->
+    <logFile>/tmp/errorprone.log</logFile>
+    <outDir>${project.build.directory}/errorprone_report</outDir>
+    <srcBaseUrl>https://github.com/unicode-org/icu/blob/main/</srcBaseUrl>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>com.google.errorprone</groupId>
+      <artifactId>error_prone_core</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>commons-cli</groupId>
+      <artifactId>commons-cli</artifactId>
+    </dependency>
+  </dependencies>
+
+  <profiles>
+    <profile>
+      <!--
+      From icu4j:
+        mvn clean test -ntp -DskipTests -DskipITs -l /tmp/errorprone.log -P errorprone
+        mvn exec:java -f tools/errorprone_report/ -DlogFile=/tmp/errorprone.log
+
+      The links to the source files go to the main GitHub repo (`main` branch).
+        But when we work locally, or in a fork / branch, the links might point to an incorrect file / line.
+        You can override the URL by passing -DsrcBaseUrl in the maven command line.
+        For local files it would be easy to do:
+          mvn exec:java -f tools/errorprone_report/ -DsrcBaseUrl=$PWD/..
+        Note: jumping to a certain line does not work on local files.
+          This is a limitation in how browsers work.
+          So opening the file in an IDE is probably more practical.
+      -->
+      <id>errorprone_report</id>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.codehaus.mojo</groupId>
+            <artifactId>exec-maven-plugin</artifactId>
+            <executions>
+              <execution>
+                <goals>
+                  <goal>java</goal>
+                </goals>
+              </execution>
+            </executions>
+            <configuration>
+              <mainClass>com.ibm.icu.dev.tool.errorprone.Main</mainClass>
+              <arguments>
+                <argument>--logFile</argument>
+                <argument>${logFile}</argument>
+                <argument>--srcBaseUrl</argument>
+                <argument>${srcBaseUrl}</argument>
+                <argument>--outDir</argument>
+                <argument>${outDir}</argument>
+              </arguments>
+            </configuration>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
+  </profiles>
+
+</project>

icu4j/tools/pom.xml

@@ -21,4 +21,17 @@
     <module>pmd</module>
   </modules>
 
+  <profiles>
+    <profile>
+      <id>requires_jdk21</id>
+      <activation>
+        <!-- Using ${enforcer.requireJavaToolsVersion} does not work. Bug? -->
+        <jdk>[21,)</jdk>
+      </activation>
+      <modules>
+        <module>errorprone_report</module>
+      </modules>
+    </profile>
+  </profiles>
+
 </project>

pom.xml

@@ -53,9 +53,17 @@
         - versions:set-property    https://www.mojohaus.org/versions/versions-maven-plugin/set-property-mojo.html
     -->
 
+    <!-- From the Maven web site, Dec. 2025 (https://maven.apache.org/docs/history.html)
+      "Maven 3.8.9 and before has now reached its end of life and is no longer supported in any way.
+      New plugin releases will require Maven 3.9.0 or later."
+    -->
+    <enforcer.requireMavenVersion>3.9.0</enforcer.requireMavenVersion>
+    <enforcer.requireJavaVersion>[11,)</enforcer.requireJavaVersion>
+    <enforcer.requireJavaToolsVersion>[21,)</enforcer.requireJavaToolsVersion>
+
     <!-- Dependencies versions -->
     <commons-cli.version>1.11.0</commons-cli.version>
-    <error_prone.version>2.25.0</error_prone.version>
+    <error_prone.version>2.49.0</error_prone.version>
     <gson.version>2.13.2</gson.version>
     <guava.version>33.5.0-jre</guava.version>
     <jmh.version>1.37</jmh.version>
@@ -438,14 +446,10 @@
               <configuration>
                 <rules>
                   <requireMavenVersion>
-                    <!-- From the Maven web site, Dec. 2025 (https://maven.apache.org/docs/history.html)
-                      "Maven 3.8.9 and before has now reached its end of life and is no longer supported in any way.
-                       New plugin releases will require Maven 3.9.0 or later."
-                    -->
-                    <version>3.9.0</version>
+                    <version>${enforcer.requireMavenVersion}</version>
                   </requireMavenVersion>
                   <requireJavaVersion>
-                    <version>[11,)</version>
+                    <version>${enforcer.requireJavaVersion}</version>
                   </requireJavaVersion>
                 </rules>
               </configuration>
@@ -656,6 +660,9 @@
            mvn clean test -DskipTests -DskipITs -P errorprone
       -->
       <id>errorprone</id>
+      <properties>
+        <enforcer.requireJavaVersion>${enforcer.requireJavaToolsVersion}</enforcer.requireJavaVersion>
+      </properties>
       <build>
         <plugins>
           <plugin>
@@ -668,11 +675,13 @@
               <!-- Use <compilerArg> to pass flags to errorprone. See https://errorprone.info/docs/flags -->
               <compilerArgs>
                 <arg>-XDcompilePolicy=simple</arg>
+                <arg>-XDaddTypeAnnotationsToSymbol=true</arg>
+                <arg>--should-stop=ifError=FLOW</arg>
                 <!--
                   WARNING: Do not wrap the line below, it will fail on Windows.
                   See https://github.com/google/error-prone/issues/4256
                 -->
-                <arg>-Xplugin:ErrorProne -Xep:UnicodeEscape:OFF -Xep:InvalidBlockTag:OFF</arg>
+                <arg>-Xplugin:ErrorProne -Xep:UnicodeEscape:OFF -Xep:InvalidBlockTag:OFF -Xep:LabelledBreakTarget:WARN</arg>
                 <arg>-Xmaxerrs</arg>
                 <arg>10000</arg>
                 <arg>-Xmaxwarns</arg>
@@ -710,6 +719,9 @@
         You can then inspect the content of the errorprone.log file, or the reports in
         the target folder (errorprone*.html, errorprone.md, errorprone.tsv) -->
       <id>errorprone-all</id>
+      <properties>
+        <enforcer.requireJavaVersion>${enforcer.requireJavaToolsVersion}</enforcer.requireJavaVersion>
+      </properties>
       <build>
         <plugins>
           <plugin>
@@ -723,6 +735,8 @@
               <!-- Use <compilerArg> to pass flags to errorprone. See https://errorprone.info/docs/flags -->
               <compilerArgs>
                 <arg>-XDcompilePolicy=simple</arg>
+                <arg>-XDaddTypeAnnotationsToSymbol=true</arg>
+                <arg>--should-stop=ifError=FLOW</arg>
                 <!--
                   -XepAllErrorsAsWarnings:
                     If we let errors be errors they fail and stop the build, so we don't get a full report.