Null and empty check. Here i am getting confused with null check.please explain me the below code?

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public boolean isValidCardDetails(CardDetailsTypeBean cardDetailsTypeBean) throws EnrollmentReqInvalidException {
        if (cardDetailsTypeBean.getCardNumber() == null || "".equals(cardDetailsTypeBean.getCardNumber())) {
            throw new EnrollmentReqInvalidException("ECDOO16", "card no is mandatory");
        }
        if (cardDetailsTypeBean.getNameOnCard() == null || "".equals(cardDetailsTypeBean.getNameOnCard())) {
            throw new EnrollmentReqInvalidException("ECDOO17", "name on card is mandatory");
        }
        if (cardDetailsTypeBean.getCvv() == 0 || "".equals(String.valueOf(cardDetailsTypeBean.getCvv()))) {
            throw new EnrollmentReqInvalidException("ECDOO18", "cvv is mandatory");
        }
        if (cardDetailsTypeBean.getExpDate() == null || "".equals(cardDetailsTypeBean.getExpDate())) {
            throw new EnrollmentReqInvalidException("ECDOO19", "exp date must be required");
        }
        return false;

    }

Well here i want to ask after getting card number and checking null,why we use "".equals there..?? can anyone explain me this? little confused?

This line of code:

cardDetailsTypeBean.getCardNumber() == null || "".equals(cardDetailsTypeBean.getCardNumber())

simply verifies if cardNumber is null or if is equal to the empty string. Empty string is different from null value, so this code checks if every field read by a getter returns a non-empty, non-null value.

How can I check for an empty/undefined/null string in JavaScript , Please note: the Mozilla link has been updated to If you need to check specifically for an empty string over null, I would think if(Boolean(str)){ // Code here } The closest thing you can get to str. just a bunch of empty spaces (I'm assuming this is for form validation) you need to do a For me that's usually strVar == "" . 5. NULL has to be tested using the IS [NOT] NULL clause NULL is NOT equal to NULL, nor is it equal to NULL. NULL implies "unknown", so it is "unknown" if NULL is equal to NULL, or NOT equal to NULL, hence you have to test for "nullity" via the IS NULL or IS NOT NULL clause, i.e.

It's superfluous, actually.

The reason for this is that the order of the equals statement on the other side of the logical comparison is guaranteed not to produce a NullPointerException, since String.equals(null) is engineered to produce false.

The reason it likely exists the way it does is that it's being made explicit that the code is checking for null and an empty string.

Bulletin of the Atomic Scientists, Paradoxically, a strong argument for "going nuclear" was the prospect that atomic Three articles discuss new goals for atomic energy in the United States,  Check for null or blank If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed.

"" isn't the same as null because "" is a String value. Your card number might instantiated with ""

null means the reference of card number has no value.

empty - Manual, A variable is considered empty if it does not exist or if its value equals FALSE return null; I'm summarising a few points on empty() with inaccessible properties, in the hope public function __get($var) { return $this->$var; } @​uses How to check empty objects and array in php code //Below line print "​Object count:1" Ahh, I see what you're getting at. The .not cases are fraught with peril if something unexpectedly becomes undefined. It's perfectly safe to use .toBeNull when you're expecting null, but not to use .not.toBeNull if you're expecting a real value. Yeah, that's a good point. 👍

FindBugs Bug Descriptions, NP: equals() method does not check for null argument, Bad practice RV: Code checks for specific values returned by compareTo Dm: A thread was created using the default empty run method Dm: Method allocates an object, only to get the class object A null pointer is dereferenced here. This will  Free Grammar Check All the grammar you need to succeed in life™ - Explore our world of Grammar with FREE grammar & spell checkers, eBooks , articles, tutorials, vocabulary games and more! Simply paste or write your text below and click Check My Writing to get feedback on your writing.

null, Consequences if done in Tcl: Doing anything with a null value becomes difficult, e.g. require any implementation to check every value for being null before acting on it. but the Tcl script becomes confused when the reserved string collides with valid data. jhh: Let me try to clarify what I was proposing in TIP 185 [L7 ]. In contrast, the model for the NULL-PLEASE clinical score was developed in a retrospective cohort study for predicting early fatal outcome. 13 The variables included in the NULL-PLEASE clinical

Generic Null/Empty check for each property of a class, In this example let me use simplified check (negative numbers are not empty and I public class SampleClass { public int Property1 { get; set; } public bool We achieve this using the following code (for this example, I am choosing to Here is where things should be done in a way that should support the following idioms:​. How do I test for null or empty value?. ASP.NET Forums on Bytes. dropdownlist is empty, nothing, or null, how do I test for this? I cannot find it. Thank you.

Comments
  • Cause you are dealing with String value. it could be null and also could be an empty string. isnt it sounds natural ?
  • Possible duplicate of What is the difference between == vs equals() in Java?
  • The conditions are checking for null first and then, if the object is initialized, they check for an empty String.
  • null means there is no instance of a object, it has not bean instantiated and does not have a values. With equals you check if the values is "" (empty), so that means that it is instantiated but its value is "" (empty).
  • Possible duplicate of Check whether a string is not null and not empty
  • It's worth noting that because of the first condition, there is literally no benefit to the Yoda condition. It should be cardDetailsTypeBean.getCardNumber().equals("")
  • Better to do the reverse: "".equals(cardDetailsTypeBean.getCardNumber()) actually performs correctly the check with no need of doing any nullcheck.
  • Or maybe using Apache Commons StringUtils.isEmpty
  • It doesn't. "".equals(null) would return false, which would not cause a failure in OP's validation.