Empty string constant in java

Check Empty String in Java

Create Empty String in Java Let’s create an empty string by assigning an empty value to it by using the empty double-quotes. Create Empty String Using Apache Library in Java If you are working with the apache commons library, you can use the class with an Empty constant to create an empty string in Java.

Check Empty String in Java

This tutorial introduces why there is no empty string constant in the Java String class and how to deal with an empty string in Java.

In Java, there is no constant that shows an empty string, and even the String class does not have such provision. So far, to use empty string, we can assign it by using empty double-quotes.

In this article, we will learn to create an empty string and then validate it with various methods to check whether the string is really empty or not. We are going to use the apache commons library and java 11 string isBlank() method. Let’s start with some examples.

Create Empty String in Java

Let’s create an empty string by assigning an empty value to it by using the empty double-quotes. It is the simplest way to do this. Java does not provide any existing constant, so we used it.

public class SimpleTesting < public static void main(String[] args)< String empty_str = ""; System.out.println(empty_str); >> 

Or we can create our own constant that refers to an empty string and then uses this constant in the code to create an empty string. In the code below, we created a static final string that holds an empty value and assigned it to the empty_str variable.

It works fine and compiles successfully without any compilation error.

public class SimpleTesting < private static final String EMPTY_STRING = ""; public static void main(String[] args)< String empty_str = EMPTY_STRING; System.out.println(empty_str); >> 

Create Empty String Using Apache Library in Java

If you are working with the apache commons library, you can use the StringUtils class with an Empty constant to create an empty string in Java. This class has a built-in empty constant so the programmer can directly use it in the code. See the example below.

import org.apache.commons.lang3.StringUtils; public class SimpleTesting < public static void main(String[] args)< String empty_str = StringUtils.EMPTY; System.out.println(empty_str); >> 

Verify Empty String Using isEmpty() Method in Java

After creating an empty string, we must verify it to check whether the string is really empty or not. For this purpose, we can use the isEmpty() method of the String class that returns True for an empty value.

This example used the isEmpty() method in the if block to execute the code conditionally.

public class SimpleTesting< private static final String EMPTY_STRING = ""; public static void main(String[] args)< String empty_str = EMPTY_STRING; if(empty_str.isEmpty()) < System.out.println("String is empty"); >else System.out.println("String is not empty"); > > 

Verify Empty String Using equals() Method in Java

equals() method in Java is used to check whether two objects are equal or not. We can use this to check empty strings by calling on an empty string and passing the argument. See the example below.

public class SimpleTesting< private static final String EMPTY_STRING = ""; public static void main(String[] args)< String empty_str = EMPTY_STRING; if ("".equals(empty_str)) < System.out.println("String is empty"); >else System.out.println("String is not empty"); > > 

Verify Empty String Using isBlank() Method in Java

Java 11 added a new method, isBlank() , to the String class. This method checks whether a string is empty or contains only white space codepoints. It returns true if the string is empty. We can use this to verify empty string. See the example below.

public class SimpleTesting< private static final String EMPTY_STRING = ""; public static void main(String[] args)< String empty_str = EMPTY_STRING; if(empty_str.isBlank()) < System.out.println("String is empty"); >else System.out.println("String is not empty"); > > 

Checking if a string is empty or null in Java [duplicate], StringUtils.isBlank(String str) — Checks if a String is whitespace, empty («») or null. the latter considers a String which consists

Checking for an Empty, Null, or Undefined String

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Duration: 3:43

JAVA String Validation: NULL , EMPTY and BLANK

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Checking for empty string using .equals(), .isEmpty() and .length() in Java

I am writing some code to check if two strings are anagrams , in Java. This is for the Anagrams problem on Hackerrank.

My code is failing only 1 of the 17 test cases, and I’m guessing it’s due to invalid inputs. This is where my issue lies. At the very beginning of the method, I want to check if either input string is null or an empty string, and if it is, I return false.

This is the relevant code block —

private static boolean isAnagram(String a, String b) < System.out.println(a + " " + b); if( a == null || b == null || a.equals("") || b.equals("") ) < System.out.println("Inside"); return false; >HashMap map1 = new HashMap<>(); HashMap map2 = new HashMap<>(); 

The problem is, when I test this method with invalid inputs, like «hello» and «» , the if block doesn’t seem to execute. I’ve tried replacing the .equals() method with .isEmpty() and .length() == 0 , but no matter which method I use, the if doesn’t work.

Using jshell , I’ve checked that if I create an empty string with «» , all these methods work —

jshell> String a = "" a ==> "" jshell> a.isEmpty() $2 ==> true jshell> a.length() $3 ==> 0 jshell> a.equals("") $4 ==> true jshell> a == null $5 ==> false jshell> "" == "" $6 ==> true jshell> jshell> "".equals("") $7 ==> true jshell> "".length() 

Is there a reason why this way of checking for empty string won’t work in an if block?

UPDATE — Complete code on Pastebin

I see that you don’t pass one test case, and it does not involve invalid inputs. You’ve missed one thing, you should take into consideration case sensitivity

a = a.toLowerCase(); b = b.toLowerCase(); 

Just make your strings lowercase after validation and it should be alright

Check Empty String in Java, Java 11 added a new method, isBlank() , to the String class. This method checks whether a string is empty or contains only white space

How to check multiple string value are empty or blank at one shot using java

I’ve scenario to validate given input param is empty or not, I’ve list of fields with datatype string and date — productId,productName,productType,productRating,productSellDate and productReturnDate

I want to check these input params are null or empty or blank for each field and if any one of the field is empty or blank or null — it should throw NullPointerException with field name.

Please find my code below — since I’m new to Java please apologize for the coding standard. I don’t know how to get the field name which has empty or null when I throw NullPointerException

And I’m calling validate and validateDate for each string, is there any option to validate all these param in one go?

Please suggest if there is any better way of writing the below piece of code. Appreciated your help in advance! Thanks.

import java.util.Date; public class Test < public static void main(String[] args) < String productId = ""; String productName = "Apple"; String productType = "Electronics"; String productRating = "Good"; Date productSellDate = new Date(); Date productReturnDate = new Date(); System.out.println(validate(productId)); System.out.println(validate(productName)); System.out.println(validate(productType)); System.out.println(validate(productRating)); System.out.println(validateDate(productSellDate)); System.out.println(validateDate(productReturnDate)); >private static String validate(String s) < if (s.isBlank() || s.isEmpty()) < throw new NullPointerException("input param is empty"); // how to get the string field name which is empty or null or blank >else < return "valid"; >> private static String validateDate(Date d) < if (d == null) < throw new NullPointerException("sell or return date is empty"); // how to get the date field name which is empty or null or blank >else < return "date is valid"; >> > 

You can write it like this to take any number of input and throw if any one fo them are null or blank or empty

private static String validate(String. strings) < for (String s : strings) < if (s == null || s.isBlank() || s.isEmpty()) < throw new NullPointerException("input param is empty"); >> return "valid"; > 

and you can call it with any number of inputs

You may consider it just a minor improvement over the solution that you have got. It certainly isn’t a one-shot validation of all the variables. My idea is to do validation and assignment of each in the same line. For example:

 String productId = validate("", "productId"); String productName = validate("Apple", "productName"); 

Exception in thread «main» java.lang.NullPointerException: productId

The message mentions that the productId is blank/empty.

This obviously requires validate() to return the validated object in the case where it doesn’t throw.

private static String validate(String s, String message) < if (s == null || s.isBlank()) < throw new NullPointerException(message); >else < return s; >> 

We don’t need isEmpty() as an explicit condition since isBlank() also returns true for the completely empty string. Whether you want to check for null , you know best yourself.

For non-String variables simply use the built-in Objects.requireNonNull() :

 LocalDate productSellDate = Objects.requireNonNull( LocalDate.now(ZoneId.systemDefault()), "productSellDate"); LocalDate productReturnDate = Objects.requireNonNull( LocalDate.now(ZoneId.systemDefault()), "productReturnDate"); 

LocalDate is a class from java.time, the modern Java date and time API that I recommend for all of your date work. A LocalDate is a date without time of day. If you need the time too, find some other class from the same API.

Checking empty string in Java, You can use the Apache Commons Lang to check a String: if (StringUtils.isBlank(

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Check Empty String in Java

1. Create Empty String in Java
2. Create Empty String Using Apache Library in Java
3. Verify Empty String Using isEmpty() Method in Java
4. Verify Empty String Using equals() Method in Java
5. Verify Empty String Using isBlank() Method in Java

This tutorial introduces why there is no empty string constant in the Java String class and how to deal with an empty string in Java.

In Java, there is no constant that shows an empty string, and even the String class does not have such provision. So far, to use empty string, we can assign it by using empty double-quotes.

In this article, we will learn to create an empty string and then validate it with various methods to check whether the string is really empty or not. We are going to use the apache commons library and Java 11 String isBlank() method. Let’s start with some examples.

Create Empty String in Java

Let’s create an empty string by assigning an empty value to it by using the empty double-quotes. It is the simplest way to do this. Java does not provide any existing constant, so we used it.

public class SimpleTesting  public static void main(String[] args)  String empty_str = "";  System.out.println(empty_str);  > > 

Or we can create our own constant that refers to an empty string and then uses this constant in the code to create an empty string. In the code below, we created a static final string that holds an empty value and assigned it to the empty_str variable.

It works fine and compiles successfully without any compilation error.

public class SimpleTesting  private static final String EMPTY_STRING = "";  public static void main(String[] args)  String empty_str = EMPTY_STRING;  System.out.println(empty_str);  > > 

Create Empty String Using Apache Library in Java

If you are working with the apache commons library, you can use the StringUtils class with an Empty constant to create an empty string in Java. This class has a built-in empty constant so the programmer can directly use it in the code. See the example below.

import org.apache.commons.lang3.StringUtils; public class SimpleTesting  public static void main(String[] args)  String empty_str = StringUtils.EMPTY;  System.out.println(empty_str);  > > 

Verify Empty String Using isEmpty() Method in Java

After creating an empty string, we must verify it to check whether the string is really empty or not. For this purpose, we can use the isEmpty() method of the String class that returns True for an empty value.

This example used the isEmpty() method in the if block to execute the code conditionally.

public class SimpleTesting  private static final String EMPTY_STRING = "";  public static void main(String[] args)  String empty_str = EMPTY_STRING;  if(empty_str.isEmpty())   System.out.println("String is empty");  >else  System.out.println("String is not empty");  > > 

Verify Empty String Using equals() Method in Java

The equals() method in Java is used to check whether two objects are equal or not. We can use this to check empty strings by calling on an empty string and passing the argument. See the example below.

public class SimpleTesting  private static final String EMPTY_STRING = "";  public static void main(String[] args)  String empty_str = EMPTY_STRING;  if ("".equals(empty_str))   System.out.println("String is empty");  >else  System.out.println("String is not empty");  > > 

Verify Empty String Using isBlank() Method in Java

Java 11 added a new method, isBlank() , to the String class. This method checks whether a string is empty or contains only white space codepoints. It returns true if the string is empty. We can use this to verify empty string. See the example below.

public class SimpleTesting  private static final String EMPTY_STRING = "";  public static void main(String[] args)  String empty_str = EMPTY_STRING;  if(empty_str.isBlank())   System.out.println("String is empty");  >else  System.out.println("String is not empty");  > > 

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