[NETBEANS-407] "Dereferencing possible null pointer" after doing instanceof on variable (false positive)

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 8.2, 9.0
• Fix Version/s: 9.0
• Component/s: java - Hints
• Labels: pull-request-available
• External issue URL: https://netbeans.org/bugzilla/show_bug.cgi?id=269324
• Assignee: Jan Lahoda
• Reporter: Eirik Bakke
• Created: 18/Feb/18 03:52
• Updated: 03/Nov/19 20:07
• Resolved: 29/Mar/18 05:19

Description

In the following example, the "boolean foo = k instanceof Integer" assignment causes a spurious "Dereferencing possible null pointer" warning to occur on the "k.doubleValue()" expression. I believe this did not happen in earlier NetBeans versions (pre-8.2). Note that if the assignment to "boolean foo" is replaced by an if statement ("if (k instanceof Integer)"), the warning goes away.

public class TestClass {
  private Number getFoo() {
    return 3;
  }

  public void testFoo() {
    Number k = getFoo();
    // The warning only occurs if this assignment is present.
    boolean foo = k instanceof Integer;
    // Warning on .doubleValue() here: "Dereferencing possible null pointer"
    System.out.println(k.doubleValue());
  }
}

This bug was previously described at https://netbeans.org/bugzilla/show_bug.cgi?id=269324 .

Issue Links

• links to: GitHub Pull Request #436