FULL PRODUCT VERSION :
1.6.0_20-64Bit SDK, IDE: IntelliJ IDEA 8.1

ADDITIONAL OS VERSION INFORMATION :
Windows 7 64Bit Professional

EXTRA RELEVANT SYSTEM CONFIGURATION :
machine: Intel I5, 4GB

A DESCRIPTION OF THE PROBLEM :
The String.indexof()-method sometimes returns an invalid value:


Code-Sample:
--------------------

public static String replaceChars(String name, String old, String newDelimiter) {
    if (name == null) return name;

    int index = name.indexOf(old);
    while (index != -1) {
      if (index == 0) {
        name = newDelimiter + name.substring(old.length());
      }
      else {
        name = name.substring(0, index) + newDelimiter + name.substring(index + old.length());
      }
      index = name.indexOf(old);
    }
    return name;
  }

________________

Problem (Example):

name.length() returns '44'

--> 'name.indexof(old)' returns '44' (!!!) -> (should return '-1' if value of variable 'old' is not included in 'name', but 44 doesn´t even exit in index-range!)

This Problem does not occur if '-Xint' is used as Parameter.

--> Assumption: It´s an optimization-problem, we had that problem in the Java-SDK-versions 1.6.0_19 and 1.6.0_20, both 64 bit.
The problem does not occur in Java-Version 1.6.0_12, 32Bit.

Info: variable-values were checked using debug-mode, the problem is non-deterministic, meaning that it cannot be reproduced in the same loop-itarations, but often occured in case of a name.length() - value of 44.





STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
run example-code (see Description):

public static String replaceChars(String name, String old, String newDelimiter) {
    if (name == null) return name;

    int index = name.indexOf(old);
    while (index != -1) {
      if (index == 0) {
        name = newDelimiter + name.substring(old.length());
      }
      else {
        name = name.substring(0, index) + newDelimiter + name.substring(index + old.length());
      }
      index = name.indexOf(old);
    }
    return name;
  }

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Example:

name.length() returns '44'

--> 'name.indexof(old)' returns '44' (!!!) -> (should return '-1' if value of variable 'old' is not included in 'name', but 44 doesn´t even exit in index-range!)
ACTUAL -
name.indexof(var) should return '-1' if value of 'var' is not included in 'name', but returns an index that´s not even in the range (see Desc.)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public static String replaceChars(String name, String old, String newDelimiter) {
    if (name == null) return name;

    int index = name.indexOf(old);
    while (index != -1) {
      if (index == 0) {
        name = newDelimiter + name.substring(old.length());
      }
      else {
        name = name.substring(0, index) + newDelimiter + name.substring(index + old.length());
      }
      index = name.indexOf(old);
    }
    return name;
  }
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
using the indexof()-method twice, it returns -1 on the second use, even if the first one, direcly performed before, returned another value:

int index:

index = name.indexof(var); --> wrong value
index = name.indexof(var); --> correct value