From 7eb090f910fe7b8aff4e91e0f50b67ca442f739e Mon Sep 17 00:00:00 2001
From: Mihai Nita <nmihai_2000@yahoo.com>
Date: Mon, 31 Mar 2025 13:19:40 -0700
Subject: [PATCH] ICU-23072 Support from JDK 11 up, drop support for JDK 8

---
 .github/workflows/icu4j.yml               |   4 +-
 .github/workflows/icu_common.yml          |   2 +-
 .github/workflows/icu_merge_ci.yml        |  62 +++---------
 .github/workflows/release-icu4j-maven.yml |   2 +-
 icu4j/main/localespi/pom.xml              | 110 +---------------------
 icu4j/pom.xml                             |  68 +++++--------
 icu4j/tools/build/pom.xml                 |  24 -----
 icu4j/tools/taglets/pom.xml               |  24 -----
 8 files changed, 43 insertions(+), 253 deletions(-)

diff --git a/.github/workflows/icu4j.yml b/.github/workflows/icu4j.yml
index 8086dc8bff6..04beeba64a0 100644
--- a/.github/workflows/icu4j.yml
+++ b/.github/workflows/icu4j.yml
@@ -60,7 +60,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: 'temurin'
-          java-version: '8'
+          java-version: '11'
       # Download all of the artifacts needed for the code and build plugins, but
       # exclude any needed by profiles depending on system artifacts
       - name: Download all artifacts
@@ -75,7 +75,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java-version: [ '8', '11', '17', '21' ]
+        java-version: [ '11', '17', '21' ]
     runs-on: ubuntu-22.04  # Updated in BRS
     steps:
       - name: Checkout and setup
diff --git a/.github/workflows/icu_common.yml b/.github/workflows/icu_common.yml
index e8b548fbe7e..59b04895a1e 100644
--- a/.github/workflows/icu_common.yml
+++ b/.github/workflows/icu_common.yml
@@ -66,7 +66,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: 'temurin'
-          java-version: '8'
+          java-version: '11'
       # Download all of the artifacts needed for the code and build plugins, but
       # exclude any needed by profiles depending on system artifacts
       - name: Download all artifacts
diff --git a/.github/workflows/icu_merge_ci.yml b/.github/workflows/icu_merge_ci.yml
index 6e401b891e8..6e1e3bd72db 100644
--- a/.github/workflows/icu_merge_ci.yml
+++ b/.github/workflows/icu_merge_ci.yml
@@ -27,11 +27,16 @@ env:
 permissions:
   contents: read
 
+# Using Java 11 because Java version not deemed significant for downloading artifacts,
+# and is the lowest version we support, so the cached artifacts can be used by any other version.
+uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
+  with:
+    distribution: 'temurin'
+    java-version: '11'
+
 jobs:
 
   # Initialize the Maven artifact cache
-  # Uses Java 8 because Java version not deemed significant for downloading
-  # artifacts
   #
   # This job is created according to the cache strategy of reuse from a single job:
   # https://github.com/actions/cache/blob/main/caching-strategies.md#make-cache-read-only--reuse-cache-from-centralized-job
@@ -49,10 +54,6 @@ jobs:
         with:
           path: ~/.m2/repository
           key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
-      - uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
-        with:
-          distribution: 'temurin'
-          java-version: '8'
       # Download all of the artifacts needed for the code and build plugins
       - name: Download all artifacts
         run: |
@@ -78,10 +79,6 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-maven-
           lookup-only: true
-      - uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
-        with:
-          distribution: 'temurin'
-          java-version: '11'
       - name: ICU4J little-endian
         run: |
           cd icu4c/source;
@@ -342,11 +339,6 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-maven-
           lookup-only: true
-      - uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
-        with:
-          distribution: 'temurin'
-          java-version: '8'
-
       - name: Build and run unicodesetperf test
         run: |
           cd icu4j;
@@ -354,9 +346,8 @@ jobs:
           git status
           cd perf-tests;
           mkdir -p perf/results/j_unicodesetperf/${{ matrix.perf }};
-          mvn dependency:copy-dependencies 
+          mvn dependency:copy-dependencies
           java -cp ./target/*:./target/dependency/* com.ibm.icu.dev.test.perf.UnicodeSetPerf ${{ matrix.perf }} -a -t 2 -p 4 [:Lt:] | tee perf/results/j_unicodesetperf/${{ matrix.perf }}/output.txt
-
       - name: Store performance test results
         uses: gregtatum/github-action-benchmark@d3f06f738e9612988d575db23fae5ca0008d3d12
         with:
@@ -400,20 +391,14 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-maven-
           lookup-only: true
-      - uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
-        with:
-          distribution: 'temurin'
-          java-version: '8'
-
       - name: Build and run ucharacterperf test
         run: |
           cd icu4j;
           mvn ${SHARED_MVN_ARGS} install -DskipITs -DskipTests;
           cd perf-tests;
           mkdir -p perf/results/j_ucharacterperf;
-          mvn dependency:copy-dependencies 
+          mvn dependency:copy-dependencies
           java -cp ./target/*:./target/dependency/* com.ibm.icu.dev.test.perf.UCharacterPerf -a -t 2 -p 4 0 ffff | tee perf/results/j_ucharacterperf/output.txt
-
       - name: Store performance test results
         uses: gregtatum/github-action-benchmark@d3f06f738e9612988d575db23fae5ca0008d3d12
         with:
@@ -460,11 +445,6 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-maven-
           lookup-only: true
-      - uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
-        with:
-          distribution: 'temurin'
-          java-version: '8'
-
       - name: Build and run decimalformatperf
         run: |
           cd icu4j;
@@ -475,9 +455,8 @@ jobs:
           # tests over 180 secs. minimizes the possibility of push conflicts when storing
           # tests results in the data branch.
           sleep $(($RANDOM % 180));
-          mvn dependency:copy-dependencies 
+          mvn dependency:copy-dependencies
           java -cp ./target/*:./target/dependency/* com.ibm.icu.dev.test.perf.DecimalFormatPerformanceTest ${{ matrix.perf }} -a -t 2 -p 4 -L ${{ matrix.locale }} "#,###.##" "1.234,56" -r 1 | tee perf/results/j_decimalformatperf/${{ matrix.locale }}/${{ matrix.perf }}/output.txt
-
       - name: Store performance test results
         uses: gregtatum/github-action-benchmark@d3f06f738e9612988d575db23fae5ca0008d3d12
         with:
@@ -525,11 +504,6 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-maven-
           lookup-only: true
-      - uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
-        with:
-          distribution: 'temurin'
-          java-version: '8'
-
       - name: Build and run normperf
         env:
           DATA_FILE_PATH: data/collation
@@ -542,7 +516,7 @@ jobs:
           # tests over 180 secs. minimizes the possibility of push conflicts when storing
           # tests results in the data branch.
           sleep $(($RANDOM % 180));
-          mvn dependency:copy-dependencies 
+          mvn dependency:copy-dependencies
           java -cp ./target/*:./target/dependency/* com.ibm.icu.dev.test.perf.NormalizerPerformanceTest ${{ matrix.perf }} -a -t 2 -p 4 -f $DATA_FILE_PATH/${{ matrix.source_text }}.txt -e UTF-8 ${{ matrix.mode }} | tee perf/results/j_normperf/${{ matrix.source_text }}/${{ matrix.perf }}/output.txt
           cat perf/results/j_normperf/${{ matrix.source_text }}/${{ matrix.perf }}/output.txt
 
@@ -660,11 +634,6 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-maven-
           lookup-only: true
-      - uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
-        with:
-          distribution: 'temurin'
-          java-version: '8'
-
       - name: Build and run converterperf
         env:
           DATA_FILE_PATH: data/conversion
@@ -677,7 +646,7 @@ jobs:
           # tests over 180 secs. minimizes the possibility of push conflicts when storing
           # tests results in the data branch.
           sleep $(($RANDOM % 180));
-          mvn dependency:copy-dependencies 
+          mvn dependency:copy-dependencies
           java -cp ./target/*:./target/dependency/* com.ibm.icu.dev.test.perf.ConverterPerformanceTest ${{ matrix.perf }} -a -t 2 -p 4 -f $DATA_FILE_PATH/${{ matrix.source_text }}.txt -e UTF-8 -T ${{ matrix.test_enc }} | tee perf/results/j_converterperf/${{ matrix.source_text }}/${{ matrix.test_enc }}/${{ matrix.perf }}/output.txt
 
       - name: Store performance test results
@@ -739,11 +708,6 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-maven-
           lookup-only: true
-      - uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
-        with:
-          distribution: 'temurin'
-          java-version: '8'
-
       - name: Extract identifying digit and parameter.
         run: |
           ddir='${{ matrix.parms }}';
@@ -759,7 +723,7 @@ jobs:
           # tests over 180 secs. minimizes the possibility of push conflicts when storing
           # tests results in the data branch.
           sleep $(($RANDOM % 180));
-          mvn dependency:copy-dependencies 
+          mvn dependency:copy-dependencies
           java -cp ./target/*:./target/dependency/* com.ibm.icu.dev.test.perf.DateFormatPerformanceTest ${{ matrix.perf }} -a -t 2 -p 4 -L ${{ matrix.locale }} ${{ env.PARM }} -r 1 | tee perf/results/j_dateformatperf/${{ matrix.locale }}/${{ matrix.perf }}/${{ env.DDIR }}/output.txt
 
       - name: Store performance test results
diff --git a/.github/workflows/release-icu4j-maven.yml b/.github/workflows/release-icu4j-maven.yml
index 33c6fa40e1d..b102ac8474a 100644
--- a/.github/workflows/release-icu4j-maven.yml
+++ b/.github/workflows/release-icu4j-maven.yml
@@ -55,7 +55,7 @@ jobs:
     - name: Set up JDK
       uses: actions/setup-java@v4.2.2
       with:
-        java-version: '8' # The custom Taglets for javadoc (tools/build) are still Java 8. They need updating to use a different JDK version.
+        java-version: '11'
         distribution: 'temurin'
         server-id: icu4j-maven-repo # Value of the distributionManagement/repository/id field of the pom.xml
         server-username: MAVEN_USERNAME # env variable for username in deploy
diff --git a/icu4j/main/localespi/pom.xml b/icu4j/main/localespi/pom.xml
index f2a956f7fad..7bafb1d5858 100644
--- a/icu4j/main/localespi/pom.xml
+++ b/icu4j/main/localespi/pom.xml
@@ -108,45 +108,13 @@
             <include>**/*IT.java</include>
             <include>**/*ITCase.java</include>
           </includes>
-
           <!--
-            For Java 8:
-            Set up the locale service provider using the .jar file of `icu4j-localespi` main code from the `package` phase
-
-            Leave empty for Java 9+.
-            Using the `java.ext.dirs` special Java system property on Java 9+ runtimes triggers an
-             error that tells the user to place those jars on the classpath instead.
-          -->
-          <!--
-              Notes:
-
-              https://stackoverflow.com/a/5039973/2077918
-              The `java.ext.dirs` is a special Java system property that activates the Java extension mechanism.
-              The Java extension mechanism was deprecated in Java 8 (users are recommended to use `-classpath` instead),
-              and the extension mechanism was removed in Java 9 altogether.
-              For backwards compatibility testing for users of the Java extension mechansim,
-              this configuration achieves the effect of having the localespi code in a .jar file that gets loaded
-              by running this test in a phase following the `package` phase in which the .jar file is created.
-
-              https://stackoverflow.com/questions/45223908/why-does-the-java-extension-mechanism-not-check-the-classpath-for-an-optional-pa
-
-              For some reason, the plugin was effectively not honoring the values as expected that were set in
-              <systemPropertyVariables>, so instead, the <argLine> value was used to set the JVM options. This
-              approach was inspired by: https://stackoverflow.com/a/48213614/2077918
-          -->
-          <argLine>${localespi-tests.jvm.args}</argLine>
-
-          <!--
-              For Java 9+:
               Configure to use the locale service provider using the .jar file of `icu4j-localespi` main code from the `package` phase
-
-              Leave empty for Java 8 to take defaults ("SPI,JRE").
               See: https://stackoverflow.com/questions/45223908/why-does-the-java-extension-mechanism-not-check-the-classpath-for-an-optional-pa
             -->
           <systemPropertyVariables>
-            <java.locale.providers>${localespi-tests.locale-providers}</java.locale.providers>
+            <java.locale.providers>CLDR,COMPAT,SPI</java.locale.providers>
           </systemPropertyVariables>
-
         </configuration>
       </plugin>
 
@@ -167,82 +135,6 @@
   </build>
 
   <profiles>
-
-    <!--
-      For testing localespi using the Java extensions feature, which last existed in Java 8.
-      ICU4J currently has a minimum supported version of 8.
-    -->
-    <profile>
-      <id>localespi-tests-java8</id>
-      <activation>
-        <jdk>(,8]</jdk>
-      </activation>
-      <properties>
-        <localespi-tests.jvm.args>-Djava.ext.dirs="${java.io.tmpdir}/ext-test-jars"</localespi-tests.jvm.args>
-        <localespi-tests.locale-providers></localespi-tests.locale-providers>
-      </properties>
-      <build>
-        <plugins>
-          <!--
-            Mainly for running localespi tests in Java 8:
-            The easiest way to get the integration tests to pass (in particular, to get the JVM that is
-            spawned with the `-Djava.ext.dirs` system property value to be interpreted properly in order
-            for the extensions jars therein to be loaded correctly) was to copy the jars needed to a
-            separate directory. (The alternative of pointing to the build directories of the respective
-            submodules didn't seem to work.)
-
-            This isn't of much use for Java 9+, in which extensions are deprecated and the regular
-            classpath is to be used instead.
-          -->
-          <plugin>
-            <artifactId>maven-dependency-plugin</artifactId>
-            <executions>
-              <execution>
-                <id>it-test-copy-localespi-extension-jars</id>
-                <phase>integration-test</phase>
-                <goals>
-                  <goal>copy</goal>
-                </goals>
-                <configuration>
-                  <artifactItems>
-                    <artifactItem>
-                      <groupId>${project.groupId}</groupId>
-                      <artifactId>icu4j</artifactId>
-                      <version>${project.version}</version>
-                      <type>${project.packaging}</type>
-                    </artifactItem>
-                    <artifactItem>
-                      <groupId>${project.groupId}</groupId>
-                      <artifactId>icu4j-localespi</artifactId>
-                      <version>${project.version}</version>
-                      <type>${project.packaging}</type>
-                    </artifactItem>
-                  </artifactItems>
-                  <!-- https://stackoverflow.com/questions/36181371/how-can-i-get-the-temp-folder-of-a-machine-running-maven -->
-                  <outputDirectory>${java.io.tmpdir}/ext-test-jars</outputDirectory>
-                </configuration>
-              </execution>
-            </executions>
-          </plugin>
-        </plugins>
-      </build>
-    </profile>
-
-    <!--
-      For testing localespi using the classpath for Java 9+, since Java extensions were
-      deprecated after Java 8.
-    -->
-    <profile>
-      <id>localespi-tests-java9</id>
-      <activation>
-        <jdk>[9,)</jdk>
-      </activation>
-      <properties>
-        <localespi-tests.jvm.args></localespi-tests.jvm.args>
-        <localespi-tests.locale-providers>CLDR,COMPAT,SPI</localespi-tests.locale-providers>
-      </properties>
-    </profile>
-
     <profile>
       <id>with_javadoc</id>
       <build>
diff --git a/icu4j/pom.xml b/icu4j/pom.xml
index fbf4e94f64c..0b0c688755c 100644
--- a/icu4j/pom.xml
+++ b/icu4j/pom.xml
@@ -43,14 +43,15 @@
 
     <module>demos</module>
     <module>samples</module>
+    <module>tools/build</module>
     <module>tools/misc</module>
+    <module>tools/taglets</module>
     <module>perf-tests</module>
   </modules>
 
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <maven.compiler.source>1.8</maven.compiler.source>
-    <maven.compiler.target>1.8</maven.compiler.target>
+    <maven.compiler.release>11</maven.compiler.release>
 
     <maven-central-repo-url>https://oss.sonatype.org</maven-central-repo-url>
     <maven-central-releases-repo-url>${maven-central-repo-url}/service/local/staging/deploy/maven2</maven-central-releases-repo-url>
@@ -198,14 +199,7 @@
         </plugin>
         <plugin>
           <artifactId>maven-compiler-plugin</artifactId>
-          <version>3.13.0</version>
-          <!-- Plugin bug, maven.compiler.* properties are not honored, see
-            https://issues.apache.org/jira/browse/MCOMPILER-545
-          -->
-          <configuration>
-            <source>${maven.compiler.source}</source>
-            <target>${maven.compiler.target}</target>
-          </configuration>
+          <version>3.14.0</version>
         </plugin>
         <plugin>
           <artifactId>maven-surefire-plugin</artifactId>
@@ -323,6 +317,9 @@
                   <requireMavenVersion>
                     <version>3.6.3</version>
                   </requireMavenVersion>
+                  <requireJavaVersion>
+                    <version>[11,)</version>
+                  </requireJavaVersion>
                 </rules>
               </configuration>
             </execution>
@@ -658,36 +655,10 @@
       </build>
     </profile>
 
-    <!-- Starting with JDK 9, the Java compiler supports the −−release version.
-      Unlike source (checking the language features) and target (the version of the classes generated),
-      this option also checks that newer APIs are not used.
-        https://maven.apache.org/plugins/maven-compiler-plugin/examples/set-compiler-release.html
-      Would be nice if the maven-compiler-plugin would filter this out below JDK 9, but it does not.
-      So we must use an auto-activated profile for this option.
-    -->
     <profile>
-      <id>newer_jdk</id>
-      <activation>
-        <jdk>[9,)</jdk>
-      </activation>
-      <modules>
-         <module>tools/build</module>
-         <module>tools/taglets</module>
-      </modules>
-      <build>
-        <plugins>
-          <plugin>
-            <artifactId>maven-compiler-plugin</artifactId>
-            <configuration>
-              <release>8</release>
-            </configuration>
-          </plugin>
-        </plugins>
-      </build>
-    </profile>
-
-    <profile>
-      <!-- mvn test -ntp -DskipTests -DskipITs -P errorprone -->
+      <!-- mvn clean test -ntp -DskipTests -DskipITs -l errorprone.log -P errorprone
+      Then inspect the content of the errorprone.log file.
+      We will have some script to convert that to a more friendly format (likely html) -->
       <id>errorprone</id>
       <build>
         <plugins>
@@ -695,11 +666,10 @@
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-compiler-plugin</artifactId>
             <configuration>
-              <source>${maven.compiler.source}</source>
-              <target>${maven.compiler.target}</target>
-              <encoding>UTF-8</encoding>
-              <!-- Use <compilerArg> to pass flags to errorprone. See https://errorprone.info/docs/flags -->
               <showWarnings>true</showWarnings>
+              <failOnError>false</failOnError>
+              <fork>true</fork>
+              <!-- Use <compilerArg> to pass flags to errorprone. See https://errorprone.info/docs/flags -->
               <compilerArgs>
                 <arg>-XDcompilePolicy=simple</arg>
                 <!--
@@ -709,6 +679,18 @@
                     The drawback is that there are not errors now, they get mixed with the real warnings.
                 -->
                 <arg>-Xplugin:ErrorProne -XepAllErrorsAsWarnings</arg>
+                <arg>-Xmaxerrs</arg>
+                <arg>10000</arg>
+                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED</arg>
+                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED</arg>
+                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED</arg>
+                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED</arg>
+                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED</arg>
+                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED</arg>
+                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED</arg>
+                <arg>-J--add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED</arg>
+                <arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED</arg>
+                <arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED</arg>
               </compilerArgs>
               <annotationProcessorPaths>
                 <path>
diff --git a/icu4j/tools/build/pom.xml b/icu4j/tools/build/pom.xml
index edee524870b..d9e8abb5800 100644
--- a/icu4j/tools/build/pom.xml
+++ b/icu4j/tools/build/pom.xml
@@ -14,28 +14,4 @@
 
   <artifactId>tools_build</artifactId>
 
-  <properties>
-    <maven.compiler.source>11</maven.compiler.source>
-    <maven.compiler.target>11</maven.compiler.target>
-  </properties>
-
-  <profiles>
-    <profile>
-      <id>newer_jdk</id>
-      <activation>
-        <jdk>[11,)</jdk>
-      </activation>
-      <build>
-        <plugins>
-          <plugin>
-            <artifactId>maven-compiler-plugin</artifactId>
-            <configuration>
-              <release>11</release>
-            </configuration>
-          </plugin>
-        </plugins>
-      </build>
-    </profile>
-  </profiles>
-
 </project>
diff --git a/icu4j/tools/taglets/pom.xml b/icu4j/tools/taglets/pom.xml
index 6c6ba9d591e..2af1bac99b4 100644
--- a/icu4j/tools/taglets/pom.xml
+++ b/icu4j/tools/taglets/pom.xml
@@ -14,28 +14,4 @@
 
   <artifactId>tools_taglets</artifactId>
 
-  <properties>
-    <maven.compiler.source>11</maven.compiler.source>
-    <maven.compiler.target>11</maven.compiler.target>
-  </properties>
-
-  <profiles>
-    <profile>
-      <id>newer_jdk</id>
-      <activation>
-        <jdk>[11,)</jdk>
-      </activation>
-      <build>
-        <plugins>
-          <plugin>
-            <artifactId>maven-compiler-plugin</artifactId>
-            <configuration>
-              <release>11</release>
-            </configuration>
-          </plugin>
-        </plugins>
-      </build>
-    </profile>
-  </profiles>
-
 </project>