changes to support building with java 21 (#305)

contrib/terraform-testing-infrastructure/timely-grafana/Dockerfile

diff --git a/contrib/terraform-testing-infrastructure/timely-grafana/Dockerfile b/contrib/terraform-testing-infrastructure/timely-grafana/Dockerfile
index bcc6759..b5386ac 100644
--- a/contrib/terraform-testing-infrastructure/timely-grafana/Dockerfile
+++ b/contrib/terraform-testing-infrastructure/timely-grafana/Dockerfile
@@ -16,6 +16,7 @@
 # specific language governing permissions and limitations
 # under the License.
 #
+
 FROM redhat/ubi8 as builder
 COPY build_output/maven /opt/apache-maven
 COPY build_output/repo /opt/apache-maven

src/main/java/org/apache/accumulo/testing/continuous/ManySplits.java

diff --git a/src/main/java/org/apache/accumulo/testing/continuous/ManySplits.java b/src/main/java/org/apache/accumulo/testing/continuous/ManySplits.java
index d28f557..920c990 100644
--- a/src/main/java/org/apache/accumulo/testing/continuous/ManySplits.java
+++ b/src/main/java/org/apache/accumulo/testing/continuous/ManySplits.java
@@ -168,7 +168,7 @@
 
         // wait for all tablets to reach the expected sum file size
         tableNames.stream().parallel().forEach(tableName -> {
-          int elapsedMillis = 0;
+          long elapsedMillis = 0;
           long sleepMillis = SECONDS.toMillis(1);
           try {
             // wait for each tablet to reach the expected sum file size

src/main/java/org/apache/accumulo/testing/randomwalk/sequential/BatchVerify.java

diff --git a/src/main/java/org/apache/accumulo/testing/randomwalk/sequential/BatchVerify.java b/src/main/java/org/apache/accumulo/testing/randomwalk/sequential/BatchVerify.java
index 594c4ab..e13f21a 100644
--- a/src/main/java/org/apache/accumulo/testing/randomwalk/sequential/BatchVerify.java
+++ b/src/main/java/org/apache/accumulo/testing/randomwalk/sequential/BatchVerify.java
@@ -53,7 +53,7 @@
 
     try (BatchScanner scanner =
         client.createBatchScanner(state.getString("seqTableName"), new Authorizations(), 2)) {
-      int count = 0;
+      long count = 0;
       List<Range> ranges = new ArrayList<>();
       while (count < numVerify) {
         long rangeStart = env.getRandom().nextInt((int) numWrites);

src/main/java/org/apache/accumulo/testing/stress/DataWriter.java

diff --git a/src/main/java/org/apache/accumulo/testing/stress/DataWriter.java b/src/main/java/org/apache/accumulo/testing/stress/DataWriter.java
index 5cc4c90..49c538f 100644
--- a/src/main/java/org/apache/accumulo/testing/stress/DataWriter.java
+++ b/src/main/java/org/apache/accumulo/testing/stress/DataWriter.java
@@ -18,27 +18,19 @@
  */
 package org.apache.accumulo.testing.stress;
 
-import java.lang.ref.Cleaner.Cleanable;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.apache.accumulo.core.client.BatchWriter;
 import org.apache.accumulo.core.client.MutationsRejectedException;
-import org.apache.accumulo.core.util.cleaner.CleanerUtil;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 public class DataWriter extends Stream<Void> implements AutoCloseable {
   private final BatchWriter writer;
   private final RandomMutations mutations;
-  private final Cleanable cleanable;
   private final AtomicBoolean closed = new AtomicBoolean(false);
 
-  private static final Logger log = LoggerFactory.getLogger(DataWriter.class);
-
   public DataWriter(BatchWriter writer, RandomMutations mutations) {
     this.writer = writer;
     this.mutations = mutations;
-    this.cleanable = CleanerUtil.unclosed(this, DataWriter.class, closed, log, writer);
   }
 
   @Override
@@ -54,9 +46,6 @@
   @Override
   public void close() {
     if (closed.compareAndSet(false, true)) {
-      // deregister cleanable, but it won't run because it checks
-      // the value of closed first, which is now true
-      cleanable.clean();
       try {
         writer.close();
       } catch (MutationsRejectedException e) {