RFR [9]8134424: BlockDataInputStream.readUTFBody: examine sizing local StringBuffer with the given length

[Chris Hegarty]

On 11 Feb 2016, at 15:59, Roger Riggs <Roger.Riggs at Oracle.com> wrote:

> Hi Chris,
> 
> ok, but can I suggest using 65535 instead of 16384, it will match the length
> of the short encoded strings in writeObjectStream.writeString.

That sounds reasonable. So the final change is:

diff --git a/src/java.base/share/classes/java/io/ObjectInputStream.java b/src/java.base/share/classes/java/io/ObjectInputStream.java
--- a/src/java.base/share/classes/java/io/ObjectInputStream.java
+++ b/src/java.base/share/classes/java/io/ObjectInputStream.java
@@ -3144,7 +3144,14 @@
          * utflen bytes.
          */
         private String readUTFBody(long utflen) throws IOException {
-            StringBuilder sbuf = new StringBuilder();
+            StringBuilder sbuf ;
+            if (utflen > 0 && utflen < Integer.MAX_VALUE) {
+                // a reasonable initial capacity based on the UTF length
+                int initialCapacity = Math.min((int)utflen, 65536);
+                sbuf = new StringBuilder(initialCapacity);
+            } else {
+                sbuf = new StringBuilder();
+            }
             if (!blkmode) {
                 end = pos = 0;
             }
-Chris.