src/java.base/share/classes/java/lang/AbstractStringBuilder.java

rev 54260 : 8221430: StringBuffer(CharSequence) constructor truncates when -XX:-CompactStrings specified

@@ -1739,6 +1739,23 @@
         if (start < 0 || start > end || end > len) {
             throw new StringIndexOutOfBoundsException(
                 "start " + start + ", end " + end + ", length " + len);
         }
     }
+
+    /**
+     * Determine the "coder" of the given CharSequence
+     */
+    static byte getCharSequenceCoder(CharSequence seq) {
+        byte coder;
+        if (seq instanceof String) {
+            coder = ((String)seq).coder();
+        } else if (seq instanceof AbstractStringBuilder) {
+            coder = ((AbstractStringBuilder)seq).getCoder();
+        } else if (COMPACT_STRINGS) {
+            coder = LATIN1;
+        } else {
+            coder = UTF16;
+        }
+        return coder;
+    }
 }