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| Summary: | Dereferencing null pointer hint fails when not using short circuit operands | ||
|---|---|---|---|
| Product: | java | Reporter: | dktcoding |
| Component: | Hints | Assignee: | Svata Dedic <sdedic> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | Keywords: | NO74, USABILITY |
| Priority: | P3 | ||
| Version: | 7.4 | ||
| Hardware: | PC | ||
| OS: | Linux | ||
| Issue Type: | DEFECT | Exception Reporter: | |
reproducible An additional defect:
boolean foo = array1 != null;
if (array.length == 1) { // <- a warning appears, provoked by array1 != null.
}
speculative values created by == and != comparison operators leak to a permanent variable state set.
OK, correction ;) Lahvac reminded me that != or == may be seen as a hint that the programmer supposes the value *might* be sometimes null; so values which are subject to != or == operator should be checked as if null was a possible value. So my example is incorrect - not a bug. |
I prepared the following snippet to help understand the problem: 0 public void function(int[] array1, int[] array2){ 1 if (array1 == null | array2 == null){ 2 throw new NullPointerException(); 3 } 4 if (array1.length != array2.length){ 5 //Do something 6 } 7 } In that code the "Dereferencing null pointer" hint appears on line 4, but if in line 2 we use the short circuit operand || the hint goes away. Anyway it's impossible for a NullPointerException to be thrown on line 4 using either | or ||. Regards Product Version = NetBeans IDE 7.4 (Build 201310111528) Operating System = Linux version 3.11.0-12-generic running on amd64 Java; VM; Vendor = 1.7.0_45 Runtime = Java HotSpot(TM) 64-Bit Server VM 24.45-b08