Android check null or empty string in Android

Question

In my trying AsyncTask I get email address from my server. In onPostExecute() I have to check is email address empty or null

Answer 1

Use TextUtils.isEmpty( someString )

String myString = null;

if (TextUtils.isEmpty(myString)) {
    return; // or break, continue, throw
}

// myString is neither null nor empty if this point is reached
Log.i("TAG", myString);

Notes

• The documentation states that both null and zero length are checked for. No need to reinvent the wheel here.
• A good practice to follow is early return.

Answer 2

From @Jon Skeet comment, really the String value is "null". Following code solved it

if (userEmail != null && !userEmail.isEmpty() && !userEmail.equals("null")) 

Answer 3

You can check it with utility method "isEmpty" from TextUtils,

isEmpty(CharSequence str) method check both condition, for null and length.

public static boolean isEmpty(CharSequence str) {
     if (str == null || str.length() == 0)
        return true;
     else
        return false;
}

Answer 4

Yo can check it with this:

if(userEmail != null && !userEmail .isEmpty())

And remember you must use from exact above code with that order. Because that ensuring you will not get a null pointer exception from userEmail.isEmpty() if userEmail is null.

Above description, it's only available since Java SE 1.6. Check userEmail.length() == 0 on previous versions.


UPDATE:

Use from isEmpty(stringVal) method from TextUtils class:

if (TextUtils.isEmpty(userEmail))

Kotlin:

Use from isNullOrEmpty for null or empty values OR isNullOrBlank for null or empty or consists solely of whitespace characters.

if (userEmail.isNullOrEmpty())
...
if (userEmail.isNullOrBlank())