Method 4 is best.
if(foo != null && foo.bar()) {
someStuff();
}
will use short-circuit evaluation, meaning it ends if the first condition of a logical AND is false.
Top answer 1 of 16
171
Method 4 is best.
if(foo != null && foo.bar()) {
someStuff();
}
will use short-circuit evaluation, meaning it ends if the first condition of a logical AND is false.
2 of 16
19
The last and the best one. i.e LOGICAL AND
if (foo != null && foo.bar()) {
etc...
}
Because in logical &&
it is not necessary to know what the right hand side is, the result must be false
Prefer to read :Java logical operator short-circuiting
Baeldung
baeldung.com › home › java › avoid check for null statement in java
Avoid Check for Null Statement in Java | Baeldung
February 20, 2026 - Here, @NonNull makes it clear that the argument cannot be null. If the client code calls this method without checking the argument for null, FindBugs would generate a warning at compile time. Developers generally rely on IDEs for writing Java code.
How and When do you guys check "null"?
Please ensure that: Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions You include any and all error messages in full You ask clear questions You demonstrate effort in solving your question/problem - plain posting your assignments is forbidden (and such posts will be removed) as is asking for or giving solutions. Trying to solve problems on your own is a very important skill. Also, see Learn to help yourself in the sidebar If any of the above points is not met, your post can and will be removed without further warning. Code is to be formatted as code block (old reddit: empty line before the code, each code line indented by 4 spaces, new reddit: https://i.imgur.com/EJ7tqek.png ) or linked via an external code hoster, like pastebin.com, github gist, github, bitbucket, gitlab, etc. Please, do not use triple backticks (```) as they will only render properly on new reddit, not on old reddit. Code blocks look like this: public class HelloWorld { public static void main(String[] args) { System.out.println("Hello World!"); } } You do not need to repost unless your post has been removed by a moderator. Just use the edit function of reddit to make sure your post complies with the above. If your post has remained in violation of these rules for a prolonged period of time (at least an hour), a moderator may remove it at their discretion. In this case, they will comment with an explanation on why it has been removed, and you will be required to resubmit the entire post following the proper procedures. To potential helpers Please, do not help if any of the above points are not met, rather report the post. We are trying to improve the quality of posts here. In helping people who can't be bothered to comply with the above points, you are doing the community a disservice. I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns. More on reddit.com
20
4
September 4, 2024[Java] How do you check if an input string is null?
You could do something like If(s != null) { // DO YOUR LOOP } else { // RETURN EMPTY STRING OR "ERROR" } not 100% on what your trying to do here Not really sure why u have public static string at the top More on reddit.com
8
3
January 6, 2021java - How to check if object is null or not except == null - Stack Overflow
I want to make method that will check if the class instance is null or not. Simply I know that i can use == null, but I want to know that is there any other way that can be implemented to check if More on stackoverflow.com
Cleanest 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
11
3
May 8, 202401:05
How should you check if a value is null? - Cracking the Java Coding ...
02:01
Safest way to validate a Java String (nulls, and blanks) 😌 - ...
08:35
Java 8 | Optional to handle null references elegantly - YouTube
04:47
JAVA String Validation: NULL , EMPTY and BLANK - YouTube
03:01
java test for null - YouTube
04:47
JAVA String Validation: How to avoid null pointer exception - NULL ...
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 - The below example demonstrates how to check if a given string is null using the == relational operator. ... // Java Program to check if // a String is Null class StringNull { // Method to check if the String is Null public static boolean ...
Reddit
reddit.com › r/javahelp › how and when do you guys check "null"?
r/javahelp on Reddit: How and When do you guys check "null"?
September 4, 2024 -
I'm 4 y experienced Java dev but still it's unclear how and when to check nullity sometimes and it happened today. Let's say there is a table called students and it has column called `last_name` which is not null.
create table students (
last_name varchar(255) not null
)
You have written validation code to ensure all required column is appeared while inserting new record and there is a method that needs last_name of students. The parameter of this method may or may not come from DB directly(It could be mapped as DTO). In this case do you check nullity of `last_name` even though you wrote validation code? Or just skip the null check since it has not null constraint?
I know this depends on where and how this method is used and i skipped the null check because i think this method is not going to be used as general purpose method only in one class scope.
Top answer 1 of 6
17
I think there are a few approaches: Check everywhere. Be super defensive, and check the inputs to essentially every function for nulls and other violated invariants Define a boundary. Try to create clear "boundaries" in your code, for example by validating all external inputs in one layer, and then allowing the layers below this to assume that their inputs are valid Use types to your advantage, e.g. by having a PhoneNumber class rather than just using a String (which indicates that the phone number has been validated), or a PendingOrder and DeliveredOrder class rather than a single Order class with an isDelivered property (which prevents you from using orders in unintended ways) YOLO. Don't have a consistent approach to validating things
2 of 6
4
Ideally you write your interfaces and methods such that they don't return nulls and your objects don't have any properties set to null (so use Optional as return type where it makes sense, and/or return 'empty' objects, primitives, or throw exceptions). Personally, if I write a public method that could return 'null', I make it explicitly clear in the name itself, for example: `getStatusDetailsOrNull()` - but typically, I would return an Optional. Outside of that, you check the contract of the method. If the method does not guarantee a non-null response, then you check it. If you don't know, then you also check for non-null. Also use a good static checker, which will flag some areas where null can occur. In your example, you can enforce the DTO to never have a null value. Make it an immutable object, and guarantee that either instance creation fails, or no DTO field is ever null. You can then add a bunch of unit tests to make sure that a future developer does not break this accidentally. I'm not a huge fan of just checking for null everywhere because it does liter your code with superfluous checks, and it communicates to others that some method could be returning null (even though the contract may state that it doesn't).
Better Programming
betterprogramming.pub › checking-for-nulls-in-java-minimize-using-if-else-edae27016474
Checking for Nulls in Java? Minimize Using “If Else” | by Itır Ege Değer | Better Programming
January 26, 2022 - In case of lists, maps etc, isEmpty() checks if the collection/map is null or have size of 0.
Wikihow
wikihow.com › computers and electronics › software › programming › java › how to check null in java (with pictures) - wikihow
How to Check Null in Java (with Pictures) - wikiHow
May 15, 2025 - You can also use “!=” to check that a value is NOT equal. ... Use an “if” statement to create a condition for the null. The result of the expression will be a boolean (true or false) value.
Java2Blog
java2blog.com › home › core java › java basics › check if object is null in java
Check if Object Is Null in Java - Java2Blog
November 29, 2023 - The most basic and efficient way to check if an object is null is by using the == operator. ... Object myObject = null;: This line declares a variable named myObject of the type Object, which is a class in Java.
DEV Community
dev.to › scottshipp › better-null-checking-in-java-ngk
Better Null-Checking in Java - DEV Community
January 11, 2019 - As a motivating example, finding a user’s zip code in their account might look similar to this in standard Java: That’s three null checks in the space of ten lines. Using my solution, which I’ve released as part of a library called Mill, the motivating example can be converted to: There would then be a single null check afterward. Or, if an empty string or another default value might be more applicable, there is an alternative getOrDefault() method.
Javatpoint
javatpoint.com › how-to-check-null-in-java
How to Check null in Java
How to Check null in Java with java tutorial, features, history, variables, object, programs, operators, oops concept, array, string, map, math, methods, examples etc.
Medium
tamerardal.medium.com › simplify-null-checks-in-java-writing-clean-code-with-apache-commons-lang-3-e7d3aea207bd
Simplify Null Checks in Java: Writing Clean Code with Apache Commons Lang 3 | by Tamer Ardal | Medium
September 18, 2024 - Two of them are the isEmpty and isNotEmpty methods. These methods check whether the object is null or empty. if (ObjectUtils.isEmpty(myObject)) { // Null or empty } if (ObjectUtils.isNotEmpty(myObject)) { // Not null or empty } Alternatively, ...
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 - public class Example { public static void main(String[] args) { // check if it is a null string String myName = null; String nullString = null; if (myName == null) { // print if the string is null System.out.println("The String = " + myName); ...
LabEx
labex.io › tutorials › java-how-to-check-if-an-object-is-null-in-java-560011
How to Check If an Object Is Null in Java | LabEx
In Java, null is a special value that indicates that a reference variable does not point to any object. Think of a variable as a box, and an object as something you put inside the box. If the box is empty, the variable is null.
Medium
medium.com › javarevisited › avoid-verbose-null-checks-b3f11afbfcc9
Avoid Explicit Null Checks. One of the more frustrating things… | by JAVING | Javarevisited | Medium
February 3, 2022 - The client will be able to choose to pass a null object instead of a null, and this will avoid having to do an explicit null check in method(). Optional Latest versions of java have a class called Optional that can be used as a way of avoiding returning nulls. It is basically an implementation of the null object pattern. By using optional on the client we can avoid passing a null. Validators, IllegalArgumentException and Business Exceptions If the caller of the function is out of our control and we cannot be confident on the value that will pass to our function there are other alternatives to the null check that maybe regardless of also being defensive are probably more business friendly and perhaps more informative.
Liberian Geek
liberiangeek.net › home › how-to/tips › how to check if an object is null in java?
How to Check if an Object is Null in Java? | Liberian Geek
February 22, 2024 - The “if/else” statements display a message over the console according to the result provided by the “==” operator. ... The “Object” class provides an “isNull()” method to check the nullability of provided data structures.
Stack Abuse
stackabuse.com › java-check-if-string-is-null-empty-or-blank
Java: Check if String is Null, Empty or Blank
February 28, 2023 - String string = "Hello there"; if (string == null || string.equals("") || string.trim().equals("")) System.out.println("String is null, empty or blank"); else System.out.println("String is neither null, empty nor blank"); In much the same fashion as the before, if the trimmed string is "", it was either empty from the get-go, or was a blank string with 0..n whitespaces: ... The Apache Commons is a popular Java library that provides further functionality.
Baeldung
baeldung.com › home › java › core java › check if all the variables of an object are null
Check If All the Variables of an Object Are Null | Baeldung
January 8, 2024 - The simplest way is using a sequence of if statements to check field by field if they are null or not and, in the end, return a combination of their results.
Reddit
reddit.com › r/learnprogramming › [java] how do you check if an input string is null?
r/learnprogramming on Reddit: [Java] How do you check if an input string is null?
January 6, 2021 -
Incredibly frustrated with this. Trying to reverse a string with this code:
public static String reverseString(String s){
String outputString = "";
for(int i = s.length()-1; i >= 0; i--){
outputString += s.charAt(i);
}
return outputString;
}Firecode.io is giving me nullpointer exception errors. My guess is I'm being given 'null' strings and am expected to return a 'null' output.
How do I do that?
I've tried "if s == null" check but that doesn't work. if(!s) check also does not work.
How do you check if something is null in Java?
Top answer 1 of 6
5
I've tried "if s == null" check but that doesn't work. Did you put that check before or after your reference to s.length and s.charAt? Also, Java requires the condition to be in parentheses, so assuming you literally had if s == null, that might be your issue. Try if (s == null) return null;
2 of 6
2
You could do something like If(s != null) { // DO YOUR LOOP } else { // RETURN EMPTY STRING OR "ERROR" } not 100% on what your trying to do here Not really sure why u have public static string at the top
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 - When working with Strings in Java, it is common to encounter situations where a String might be either null or empty. This can lead to unexpected errors, particularly when working with user input, API responses, or database records. To avoid these issues, performing proper checks before using a String in operations like concatenation, comparison, or storage is essential. One of the most common ways to ensure a String is valid before using it is by checking if(name != null && !name.isEmpty()).
Quora
quora.com › What-is-the-best-way-to-check-if-a-variable-is-null-before-trying-to-access-its-value-in-Java
What is the best way to check if a variable is null before trying to access its value in Java? - Quora
Answer (1 of 5): I̲n̲ ̲J̲a̲v̲a̲ ̲,̲ ̲t̲h̲e̲ ̲s̲t̲a̲n̲d̲a̲r̲d ̲w̲a̲y ̲i̲s̲ ̲t̲o̲ ̲j̲u̲st̲ ̲d̲o̲ ̲a̲ ̲s̲t̲r̲a̲i̲g̲h̲t̲f̲o̲r̲w̲a̲r̲d̲ ̲n̲u̲l̲l̲ ̲c̲h̲e̲c̲k̲ ̲w̲i̲t̲h̲ ̲`̲i̲f̲ ̲(̲v̲a̲r̲i̲a̲b̲l̲e̲ ̲=̲=̲ ...
Top answer 1 of 2
56
The easiest way to check is entity == null. There is no shorter way to do that.
Note that there is a method for this in the standard lib:
Objects.isNull(Object obj)
And another one which is the opposite of the above one:
Objects.nonNull(Object obj)
And there is yet another one which can be used to force a value to be not null, it throws a NullPointerException otherwise:
T Objects.requireNonNull(T obj);
Note: The Objects class was added in Java 7, but the isNull() and nonNull() methods were added only in Java 8.
2 of 2
0
try this using reflection
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.Objects;
public class ObjectsUtils {
public static boolean allNull(Object target) {
return Arrays.stream(target.getClass()
.getDeclaredFields())
.peek(f -> f.setAccessible(true))
.map(f -> getFieldValue(f, target))
.allMatch(Objects::isNull);
}
private static Object getFieldValue(Field field, Object target) {
try {
return field.get(target);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
}
}