From d6a1f2e24d10a6d762321ebfc01a4ef3236f9303 Mon Sep 17 00:00:00 2001
From: wuwen <wuwen.55@aliyun.com>
Date: Sun, 8 Oct 2023 16:31:26 +0800
Subject: [PATCH] fixes GitHub Issue 462 (Internal class issues in the Java 21)

---
 src/main/javassist/bytecode/ConstPool.java | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/main/javassist/bytecode/ConstPool.java b/src/main/javassist/bytecode/ConstPool.java
index e8434dce..605c4eed 100644
--- a/src/main/javassist/bytecode/ConstPool.java
+++ b/src/main/javassist/bytecode/ConstPool.java
@@ -671,6 +671,9 @@ public String getStringInfo(int index)
      */
     public String getUtf8Info(int index)
     {
+        if (index == 0)
+            return null;
+        
         Utf8Info utf = (Utf8Info)getItem(index);
         return utf.string;
     }
@@ -1200,6 +1203,9 @@ public int addDoubleInfo(double d)
      */
     public int addUtf8Info(String utf8)
     {
+        if (utf8 == null)
+            return 0;
+        
         return addItem(new Utf8Info(utf8, numOfItems));
     }