You may also understand the difference between null and an empty string this way:
Original image by R. Sato (@raysato)
Answer from mikiqex on Stack Overflow Top answer 1 of 16
408
You may also understand the difference between null and an empty string this way:
Original image by R. Sato (@raysato)
2 of 16
251
"" is an actual string, albeit an empty one.
null, however, means that the String variable points to nothing.
a==b returns false because "" and null do not occupy the same space in memory--in other words, their variables don't point to the same objects.
a.equals(b) returns false because "" does not equal null, obviously.
The difference is though that since "" is an actual string, you can still invoke methods or functions on it like
a.length()
a.substring(0, 1)
and so on.
If the String equals null, like b, Java would throw a NullPointerException if you tried invoking, say:
b.length()
If the difference you are wondering about is == versus equals, it's this:
== compares references, like if I went
String a = new String("");
String b = new String("");
System.out.println(a==b);
That would output false because I allocated two different objects, and a and b point to different objects.
However, a.equals(b) in this case would return true, because equals for Strings will return true if and only if the argument String is not null and represents the same sequence of characters.
Be warned, though, that Java does have a special case for Strings.
String a = "abc";
String b = "abc";
System.out.println(a==b);
You would think that the output would be false, since it should allocate two different Strings. Actually, Java will intern literal Strings (ones that are initialized like a and b in our example). So be careful, because that can give some false positives on how == works.
CodeGym
codegym.cc › java blog › strings in java › java: check if string is null, empty or blank
Java: Check if String is Null, Empty or Blank
October 11, 2023 - The String = null The String = Lubaina Khan · “An empty String in Java means a String with length equal to zero.” If a String is empty that means the reference variable is referring to a memory location holding a String of length equal to zero.
Java: difference between String a = null and String a = new String() - Software Engineering Stack Exchange
It's a pretty naive question to ask but I got this doubt while programming for Android. I use to initialize my new strings like String a=null, so in my code there remains a probability to get More on softwareengineering.stackexchange.com
Best Way to Check if a String is Null or Empty in Java - TestMu AI Community
What is the best way to check if a String is null or empty in Java? I’m currently parsing HTML data, and sometimes the String can be null or empty when the expected word doesn’t match. To handle this, I wrote the follow… More on community.testmuai.com
0
March 19, 2025Cleanest way to check for null on a String?
If all you're doing is returning an Optional, use the features of the Optional: return Optional.ofNullable(someObject.get("someKey")); If you need to do some additional processing on the string value, call .map() on the Optional. More on reddit.com
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May 8, 2024Does it make sense to initialize a string as null instead of as an empty string?
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January 15, 2023Videos
04:47
JAVA String Validation: How to avoid null pointer exception - NULL ...
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Safest way to validate a Java String (nulls, and blanks) 😌 - ...
04:47
JAVA String Validation: NULL , EMPTY and BLANK - YouTube
02:36
Java String Declaration and Initialization, Null String - YouTube
08:35
Java 8 | Optional to handle null references elegantly - YouTube
Reddit
reddit.com › r/learnjava › does it make sense to initialize a string as null instead of as an empty string?
r/learnjava on Reddit: Does it make sense to initialize a string as null instead of as an empty string?
January 15, 2023 -
I was using IntelliJ and it said that a string needed to be initialized in order for the program to work. It suggests I initialize it this way
String example = null;
instead of
String example = "";
Do you agree with this? I've found conflicting information as to whether or not this is a good idea.
Top answer 1 of 9
9
The classical answer: it depends. Nulls and empty strings may present different meanings if viewed from the business logic perspective. That being said, a nullable value at the boundary of a method/module/library/etc should be presented as an Optional.
2 of 9
4
It depends entirely on the method (including whether or not initialisation is needed).
Oracle
docs.oracle.com › javaee › 7 › tutorial › bean-validation002.htm
21.2 Validating Null and Empty Strings - Java Platform, Enterprise Edition: The Java EE Tutorial (Release 7)
A null string is represented by null. It can be described as the absence of a string instance. Managed bean elements represented as a JavaServer Faces text component such as inputText are initialized with the value of the empty string by the JavaServer Faces implementation.
GeeksforGeeks
geeksforgeeks.org › java › program-to-check-if-the-string-is-null-in-java
Program to check if the String is Null in Java - GeeksforGeeks
July 12, 2025 - To check if a string is null in Java, we can use the "==" operator that directly compares the string reference with null.
Top answer 1 of 3
11
First let's clarify something: You mention that after assigning null to the variable you could forget to initialize it, but by assigning null to it you are in effect initializing it.
public static void main (String args[]){
String s;
System.out.println(s); // compiler error variable may not be initialized
}
vs
public static void main (String args[]){
String s=null;
System.out.println(s); // no compiler error
System.out.println(s.equals("helo")); // but this will generate an exception
}
So after you do String s=null; there's is no way that you could forget to initialize because you did initialize it.
That being clear, I would recommend you to use a "smart default". In your case perhaps the empty string "" would be a good default value if you want to avoid NullPointerException. In the other hand, sometimes it is desirable that the program produce an exception because it indicates something wrong happened under the hood that should not have happened.
2 of 3
8
In general you want to keep declaration and initialisation as close as possible to minimise exactly the type of problem you're talking about.
There is also the issue of redundant initialisation where the value null you're assigning is never used which is extra code that harms readability even if the redundant assignment is optimised away by the compiler.
Sometimes assigning some sort of default value is unavoidable, for example if you declare before a try catch, initialise inside and use it afterwards. For other types you can often find a more natural default value such as an empty list.
Medium
medium.com › @ecetasci.iu › checking-for-null-or-empty-strings-in-java-19518fa1e553
Checking for Null or Empty Strings in Java | by Ece Tasci | Medium
February 25, 2025 - In Java, calling a method on a null reference will result in a NullPointerException, one of the most common runtime errors. To prevent this, it is crucial to check for null before performing operations on a variable. An empty String ("") has zero characters but still exists in memory, specifically in the heap where Java stores objects.
Baeldung
baeldung.com › home › java › java string › checking for empty or blank strings in java
Checking for Empty or Blank Strings in Java | Baeldung
January 8, 2024 - Like Guava, it won’t check if a string only contains whitespace but checks whether a given string is null or empty. There are several ways to check whether a string is empty or not. Often, we also want to check if a string is blank, meaning that it consists of only whitespace characters. The most convenient way is to use Apache Commons Lang, which provides helpers such as StringUtils.isBlank. If we want to stick to plain Java, we can use a combination of String#trim with either String#isEmpty or String#length.
Coderanch
coderanch.com › t › 522022 › java › parse-null-string-null
How to parse null string to null. (Beginning Java forum at Coderanch)
December 30, 2010 - Yes this is the code I currently use. I am convinced I have seen some method once, that does the same thing. Perhaps it was in the Apache commons library. We allow users of our custom logging application to provide a "null" string in a property file, to express they actually mean null (no value).
TestMu AI Community
community.testmuai.com › ask a question
Best Way to Check if a String is Null or Empty in Java - TestMu AI Community
March 19, 2025 - What is the best way to check if a String is null or empty in Java? I’m currently parsing HTML data, and sometimes the String can be null or empty when the expected word doesn’t match. To handle this, I wrote the following check: if(string.equals(null) || string.equals("")){ Log.d("iftrue", "seem to be true"); }else{ Log.d("iffalse", "seem to be false"); } However, when I remove string.equals(""), the condition doesn’t work correctly.
Baeldung
baeldung.com › home › java › java string › difference between null and empty string in java
Difference Between null and Empty String in Java | Baeldung
April 19, 2024 - By default, Java initializes reference variables with null values and primitives with default values based on their type. As a result, we cannot assign null to primitives. If we assign null to a String object, it’s initialized but not instantiated and hence holds no value or reference.
Codemia
codemia.io › knowledge-hub › path › checking_if_a_string_is_empty_or_null_in_java
Checking if a string is empty or null in Java
Enhance your system design skills with over 120 practice problems, detailed solutions, and hands-on exercises
Coderanch
coderanch.com › t › 366334 › java › null-String-String-null
null String vs String null (Servlets forum at Coderanch)
September 24, 2008 - Here is the problem: A jsp has a parameter named, say, power, in its form. Upon POST, a servlet gets the value via However, if the parameter "power" happens to be a null string (as depicted in above code), then mypower is not null, but it is a true String with value "null".
DataCamp
datacamp.com › doc › java › null
null Keyword in Java: Usage & Examples
The null keyword in Java is a literal that represents a null reference, one that points to no object. It is often used to indicate that a reference variable does not currently refer to any object or that a method has no return value. The null keyword can be assigned to any reference type variable, ...
Vultr Docs
docs.vultr.com › java › examples › check-if-a-string-is-empty-or-null
Java Program to Check if a String is Empty or Null | Vultr Docs
December 17, 2024 - Similar to the previous example, this function returns true if str is null or its length is zero. Using this one line enhances readability and reduces code complexity. Understand that the Apache Commons Lang library provides enhanced string handling utilities.
BeginnersBook
beginnersbook.com › 2022 › 10 › check-if-string-is-null-empty-or-blank-in-java
Check if String is Null, Empty or Blank in Java
January 7, 2023 - String myString = null; //null string if(myString==null){ System.out.println("This is a null string"); }
Quora
quora.com › How-do-perform-a-Null-check-for-string-in-Java
How do perform a Null check for string in Java? - Quora
Answer (1 of 7): 4 Ways to check if String is null or empty in Java:- Here are my four solutions for this common problem. Each solution has their pros and cons and a special use case e.g. first solution can only be used from JDK7 on wards, second solution is the fastest way to check string is em...
Reddit
reddit.com › r/java › cleanest way to check for null on a string?
Cleanest way to check for null on a String? : r/java
May 8, 2024 - D is correct by chance : you switch the String.valueOf() call to obj.toString and I had to look the doc "if the argument is null, then a string equal to "null"; otherwise, the value of obj.toString() is returned." If it was a pure replacement I would raise an eyebrow during code review, but that code is 100% correct. [EDIT] Why are you even converting unknown type of elements into String? In real-life situations, I would recheck the requirements. ... News, Technical discussions, research papers and assorted things of interest related to the Java programming language NO programming help, NO learning Java related questions, NO installing or downloading Java questions, NO JVM languages - Exclusively Java
Upwork
upwork.com › resources › articles › {name}
Null in Java: Understanding the Basics - Upwork
August 5, 2024 - Use annotations: Utilize annotations ... The java.lang.NullPointerException is a runtime exception thrown in Java when an application attempts to use an object reference that has not been initialized (i.e., it is ...
W3Schools
w3schools.com › java › ref_string_isempty.asp
Java String isEmpty() Method
This method returns true if the string is empty (length() is 0), and false if not. ... If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail: sales@w3schools.com · If you want to report an ...