learning java Objects.requireNonNull 當傳入參數為null時，該方法返回參數本身

        System.out.println(Objects.hashCode(obj));
        System.out.println(Objects.toString(obj));
        System.out.println(Objects.requireNonNull(obj, "obj參數不能為空"));

output:

0
null
Exception in thread "main" java.lang.NullPointerException: obj參數不能為空
    at java.base/java.util.Objects.requireNonNull(Objects.java:246)
    at ObjectTest.main(ObjectTest.java:9)