Java 三元表达式空指针异常

场景

• JDK 8/21
• 业务使用三元表达式，获取结果抛出空指针

public static void main(String[] args) {
        Integer source = 1;
        Integer result = Objects.nonNull(source) ? getTarget() : 2;
        System.out.println(result);
    }

    private static Integer getTarget() {
        return null;
    }

异常

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because the return value of "com.test.service.NullPointService.getTarget()" is null
	at com.record.service.NullPointService.main(NullPointService.java:32)

原因

• JDK 底层会进行拆装箱，当null 进行 int转化，则会有空指针异常，所有包装类都会触发。
• 详细参考
  • https://docs.oracle.com/javase/specs/jls/se14/html/jls-5.html#jls-5.1.7
  • https://docs.oracle.com/javase/specs/jls/se14/html/jls-5.html#jls-5.1.8
  • https://docs.oracle.com/javase/specs/jls/se14/html/jls-15.html#jls-15.25

处理

• 显示判定

  if (Objects.nonNull(source)) {
      if (Objects.isNull(target)) {
          log.error("target is null");
      }
  }

• 指定类型, 避免触发分支预测时的拆装箱情况

  Integer result = Objects.nonNull(source) ? Optional.ofNullable(target).orElse(null) : Integer.valueOf(2);
  log.info("source:{}, target:{} , result:{}", source, target, result);

代码记录

Code: https://github.com/swzxsyh/Case
Rivision Num: 9e5a514b6f9e57ed18c0989c9f05e22f3bb7b59a