/var/tmp $ javac Test.java

/var/tmp $ cat config.xml
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
        "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
  <module name="TreeWalker">
    <module name="UnnecessaryNullCheckWithInstanceOf"/>
  </module>
</module>

/var/tmp $ cat Test.java
package com.puppycrawl.tools.checkstyle;

import java.util.Objects;

public class Test {
    public void processData(Object data, String s, String b, String getData) {
        boolean result = false;
        while (getData!= null && getData instanceof String) {
           result = true;
        }
        if (data != null && (!Objects.equals(s, b) || data instanceof String)) {  // false-negative
            boolean isValid = b != null && (s != null || b instanceof String);    //  false-negative
        }

    }
}


/var/tmp $ RUN_LOCALE="-Duser.language=en -Duser.country=US"
/var/tmp $ java $RUN_LOCALE -jar checkstyle-10.24.0-SNAPSHOT-all.jar -c config.xml Test.java
Starting audit...
[ERROR] C:\Users\anmol\IdeaProjects\checkstyle3\src\main\java\com\puppycrawl\tools\checkstyle\Test.java:8:16: Unnecessary nullity check with instanceof operator in conditional expression. [UnnecessaryNullCheckWithInstanceOf]
Audit done.
Checkstyle ends with 1 errors.