From 4aeb5ccc770c38608e7628c3603c7490b00b02e8 Mon Sep 17 00:00:00 2001
From: Dongjoon Hyun <dongjoon@apache.org>
Date: Wed, 28 Jun 2023 20:31:15 -0700
Subject: [PATCH] GH-35053: [Java] Fix MemoryUtil to support Java 21

---
 .../main/java/org/apache/arrow/memory/util/MemoryUtil.java | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/java/memory/memory-core/src/main/java/org/apache/arrow/memory/util/MemoryUtil.java b/java/memory/memory-core/src/main/java/org/apache/arrow/memory/util/MemoryUtil.java
index 70e1a2586f2..b83adf9271d 100644
--- a/java/memory/memory-core/src/main/java/org/apache/arrow/memory/util/MemoryUtil.java
+++ b/java/memory/memory-core/src/main/java/org/apache/arrow/memory/util/MemoryUtil.java
@@ -54,6 +54,10 @@ public class MemoryUtil {
    */
   public static final boolean LITTLE_ENDIAN = ByteOrder.nativeOrder() == ByteOrder.LITTLE_ENDIAN;
 
+  // Java 1.8, 9, 11, 17, 21 becomes 1, 9, 11, 17, and 21.
+  private static final int majorVersion =
+      Integer.parseInt(System.getProperty("java.specification.version").split("\\D+")[0]);
+
   static {
     try {
       // try to get the unsafe object
@@ -94,7 +98,8 @@ public Object run() {
               @Override
               public Object run() {
                 try {
-                  final Constructor<?> constructor =
+                  final Constructor<?> constructor = (majorVersion >= 21) ?
+                      direct.getClass().getDeclaredConstructor(long.class, long.class) :
                       direct.getClass().getDeclaredConstructor(long.class, int.class);
                   constructor.setAccessible(true);
                   logger.debug("Constructor for direct buffer found and made accessible");