Android Check Null or Empty String in Android

Android check null or empty string in Android

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

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

how to check if a string is empty or null in Android Studio

Just Use

if(TextUtils.isEmpty(/* your String*/)){
  // String is empty or null
}else {
  // string has value
}

How to check a string that not empty in java?

You can see if the characters match

if (str.equals ("")) {
  // true
}

if (str3.equals ("   ")) {
  // true
}

Check the null values in android edit text

You can check null values from the both by following code :

Signbutton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {

        final ProgressDialog mdialog = new ProgressDialog(signin.this);
        mdialog.setMessage("please waiting...");

       if (!TextUtils.isEmpty(editphone.getText.toString.trim()) && !TextUtils.isEmpty(editpassword.getText.toString.trim())) {

        table_user.addListenerForSingleValueEvent(new ValueEventListener() {

            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                if(dataSnapshot.child(editphone.getText().toString()).exists())
                {
                    mdialog.dismiss();
                    user userobj = dataSnapshot.child(editphone.getText().toString()).getValue(user.class);

                    if (userobj.getPassword().equals(editpassword.getText().toString())) {
                        Toast.makeText(getApplicationContext(), "Sign in successfully", Toast.LENGTH_SHORT).show();
                    } else {
                        Toast.makeText(getApplicationContext(), "Sign in failed", Toast.LENGTH_SHORT).show();
                    }
                }
                else
                    {

                    Toast.makeText(getApplicationContext(), "user is not exist", Toast.LENGTH_SHORT).show();
                }

            }
            }
            } 

Check if multiple strings are empty or not without using if and when

You can make one generic function to check all string are valid or not.

You can take n number of strings as vararg and can check each of them by making one util or extension function.

Here is Util class

object StringUtils {

fun isAllValid(vararg args: String?) : Boolean {

    //checking all strings passed and if a single string is not valid returning false.
    args.forEach {
        if(isNotValid(it))
            return false
    }
    return true
}

fun isValid(string: String?): Boolean {
    return string != null && string.isNotEmpty() && string.isNotBlank()
}

fun isNotValid(string: String?) : Boolean {
    return isValid(string).not()
}

}

and you can use like this

fun changeUserAccount(
        userName: String,
        password: String,
        confirmPassword: String,
        realName: String,
        accountEmail: String,
        applicationContext: Context
    ) {

        //You can pass n number of strings.
        val isAllStringsValid = StringUtils.isAllValid(userName,password,confirmPassword,realName,accountEmail)

       //this returns true
       StringUtils.isAllValid("hi","how","are","you","?")


       //this returns false
       StringUtils.isAllValid("","how","are","you","?")


       //this returns false
       StringUtils.isAllValid(null,"how","are","you","?")


       //this returns false
       StringUtils.isAllValid("","how","are","you","?")
    }

java.lang.NumberFormatException: empty String in Android

Kindly do below changes, i.e. do trimming of string for space.

String totalOutMekanik = edTotalOutMekanik.getText().toString().trim();
String totalInMekanik = edTotalInMekanik.getText().toString().trim();

If you look official document of the {string}.isEmpty()then you find just looks length of the string and tells wether it has value or not. It does not consider spaces. In your case I guess space was causing problem.

How do I check if my EditText fields are empty?

I did something like this once;

EditText usernameEditText = (EditText) findViewById(R.id.editUsername);
sUsername = usernameEditText.getText().toString();
if (sUsername.matches("")) {
    Toast.makeText(this, "You did not enter a username", Toast.LENGTH_SHORT).show();
    return;
}

how to check the string array is empty or null android?

Very precisely

if(k!=null && k.length>0){
    System.out.println(k.length);
}else
    System.out.println("Array is not initialized or empty");

k!=null would check array is not null. And StringArray#length>0 would return it is not empty[you can also trim before check length which discard white spaces].

Some related popular question -

• What is null in java?
• Avoiding “!= null” statements in Java?

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