FULL PRODUCT VERSION :
java version "1.5.0_07"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_07-b03)
Java HotSpot(TM) Client VM (build 1.5.0_07-b03, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Linux ghost 2.6.15-23-386 #1 PREEMPT Tue May 23 13:49:40 UTC 2006 i686 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
find() behaves differently between 1.4 and 1.5 for the Matcher when the character sequence is modified in size.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
compile and run reg15.java that I provided below with a JRE 1.4.2_04 and with a JRE 1.5.0_07.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
using:
java version "1.4.2_04"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_04-b05)
Java HotSpot(TM) Client VM (build 1.4.2_04-b05, mixed mode)


a matches: 'a' in: 'bacadav'
a matches: 'a' in: 'bcadav'
a matches: 'a' in: 'bcdav'
a matches: 'a' in: 'bcdv'
ACTUAL -
a matches: 'b' in: 'bacadav'
a matches: 'c' in: 'bcadav'
a matches: 'd' in: 'bcdav'
a matches: 'v' in: 'bcdv'
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 4
        at java.lang.StringBuffer.charAt(StringBuffer.java:163)
        at java.util.regex.Pattern$SingleA.match(Pattern.java:3370)
        at java.util.regex.Pattern$Start.match(Pattern.java:3019)
        at java.util.regex.Matcher.search(Matcher.java:1092)
        at java.util.regex.Matcher.find(Matcher.java:528)
        at reg15.main(reg15.java:10)

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 4
        at java.lang.StringBuffer.charAt(StringBuffer.java:163)
        at java.util.regex.Pattern$SingleA.match(Pattern.java:3370)
        at java.util.regex.Pattern$Start.match(Pattern.java:3019)
        at java.util.regex.Matcher.search(Matcher.java:1092)
        at java.util.regex.Matcher.find(Matcher.java:528)
        at reg15.main(reg15.java:10)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.util.regex.*;
import java.lang.StringBuffer;

public class reg15 {
    public static void main(String[] args) {
    String regex = "a";
    Pattern pat = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);
    StringBuffer sb = new StringBuffer("abacadav");
    Matcher mat = pat.matcher(sb);
            while (mat.find()){
                sb.delete(mat.start(),mat.end());
                System.out.println(regex + " matches: '" + mat.group() + "' in: '" + sb + "'");
            }
        }

}

---------- END SOURCE ----------