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

My simple solution to test if a string is null:

if (s.equals("null")){ ..... }

There are two cases.

The variable (of type String) is null(doesn't exists): == works.

The variable has a null value, *.equals("null") gives te right boolean value.

See the picture.

Answer 2

All you can do is to call equals() method on empty String literal and pass the object you are testing as shown below :

 String nullString = null;
 String empty = new String();
 boolean test = "".equals(empty); // true 
 System.out.println(test); 
 boolean check = "".equals(nullString); // false 
 System.out.println(check);

Answer 3

if you check null or empty String so you can try this

if (createReminderRequest.getDate() == null && createReminderRequest.getDate().trim().equals("")){
    DialogUtility.showToast(this, ProjectUtils.getString(R.string.please_select_date_n_time));
}

Answer 4

This worked for me

EditText   etname = (EditText) findViewById(R.id.etname);
 if(etname.length() == 0){
                    etname.setError("Required field");
                }else{
                    Toast.makeText(getApplicationContext(),"Saved",Toast.LENGTH_LONG).show();
                }

or Use this for strings

String DEP_DATE;
if (DEP_DATE.equals("") || DEP_DATE.length() == 0 || DEP_DATE.isEmpty() || DEP_DATE == null){
}

Answer 5

Checking for empty string if it is equal to null, length is zero or containing "null" string

public static boolean isEmptyString(String text) {
        return (text == null || text.trim().equals("null") || text.trim()
                .length() <= 0);
    }

Answer 6

Incase all the answer given does not work, kindly try

String myString = null;

if(myString.trim().equalsIgnoreCase("null")){
    //do something
}