ADDITIONAL SYSTEM INFORMATION :
OS: Microsoft Windows 11 Business / 10.0.26100 build 26100
Java runtime:
openjdk version "21.0.7" 2025-04-15 LTS
OpenJDK Runtime Environment Microsoft-11369940 (build 21.0.7+6-LTS)
OpenJDK 64-Bit Server VM Microsoft-11369940 (build 21.0.7+6-LTS, mixed mode, sharing)

A DESCRIPTION OF THE PROBLEM :
Writing a method that safetly sums two Numerics (namely Double, Float, Integer and Long), using a ternary operator to return null in case of sum of two nulls, behaves unexpectedly, generating an NPE.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run and compile the given source code
javac SumUtils.java
java SumUtils

EXPECTED VS ACTUAL BEHAVIOR
EXPECTED -
null
ACTUAL -
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.lang.Double.doubleValue()" because "<parameter2>" is null
        at SumUtils.safeSum(SumUtils.java:9)
        at SumUtils.main(SumUtils.java:5)

---------- BEGIN SOURCE ----------
public class SumUtils {
  private SumUtils() {}
  
  public static void main(String... args) {
    System.out.println(safeSum(null, null));
  }

  static Double safeSum(Double a, Double b) {
    return a == null ? b
         : b == null ? a
         : a + b;
  }
}
---------- END SOURCE ----------