Best way to check for null values in Java

Question

Before calling a function of an object  I need to check if the object is null  to avoid throwing a NullPointerException   What is the best way to go about this  I ve considered these methods   Which one is the best programming practice for Java      Method 1 if  foo    null        if  foo bar              etc                Method 2 if  foo    null   foo bar     false        etc          Method 3 try       if  foo bar              etc            catch  NullPointerException e          Method 4 -- Would this work  or would it still call foo bar    if  foo    null  amp  amp  foo bar          etc

User · Answer

As others have said  4 is the best method when not using a library method  However you should always put null on the left side of the comparison to ensure you don t accidentally assign null to foo in case of typo  In that case the compiler will catch the mistake      You meant to do this if foo    null       But you made a typo like this which will always evaluate to true if foo   null      Do the comparison in this way if null    foo      So if you make the mistake in this way the compiler will catch it if null   foo       obviously the typo is less obvious when doing an equality comparison but it s a good habit either way if foo    null   if foo    null

User · Answer

Method 4 is my preferred method   The short circuit of the  amp  amp  operator makes the code the most readable   Method 3  Catching NullPointerException  is frowned upon most of the time when a simple null check would suffice

User · Answer

Do not catch NullPointerException  That is a bad practice  It is better to ensure that the value is not null  Method  4 will work for you  It will not evaluate the second condition  because Java has short-circuiting  i e   subsequent conditions will not be evaluated if they do not change the end-result of the boolean expression   In this case  if the first expression of a logical AND evaluates to false  subsequent expressions do not need to be evaluated

User · Answer

if you do not have an access to the commons apache library  the following probably will work ok  if null    foo  amp  amp  foo bar        do something

User · Answer

Your last proposal is the best       if  foo    null  amp  amp  foo bar          etc        Because    It is easier to read  It is safe   foo bar   will never be executed if foo    null  It prevents from bad practice such as catching NullPointerExceptions  most of the time due to a bug in your code  It should  execute as fast or even faster than other methods  even though I think it should be almost impossible to notice it

User · Answer

If at all you going to check with double equal      then check null with object ref like   if null    obj     instead of   if obj    null    because if you mistype single equal  if obj   null  it will return true  assigning object returns success  which is  true  in value

User · Answer

Method 4 is far and away the best as it clearly indicates what will happen and uses the minimum of code   Method 3 is just wrong on every level  You know the item may be null so it s not an exceptional situation it s something you should check for   Method 2 is just making it more complicated than it needs to be   Method 1 is just method 4 with an extra line of code

User · Answer

We can use Object requireNonNull static method of Object class  Implementation is below  public void someMethod SomeClass obj        Objects requireNonNull obj   Validation error  obj cannot be null

User · Answer

Simple one line Code to check for null    namVar    null   codTdoForNul     codTdoForFul

User · Answer

Method 4 is best   if foo    null  amp  amp  foo bar         someStuff        will use short-circuit evaluation  meaning it ends if the first condition of a logical AND is false

User · Answer

In Java 7  you can use Objects requireNonNull    Add an import of Objects class from java util   public class FooClass                 public void acceptFoo Foo obj              If obj is null  NPE is thrown         Objects requireNonNull obj  bar      or better requireNonNull obj   obj is null

User · Answer

For java 11  you can use Objects nonNull Object obj  if nonNull foo

User · Answer

If you control the API being called  consider using Guava s Optional class  More info here  Change your method to return an Optional lt Boolean gt  instead of a Boolean   This informs the calling code that it must account for the possibility of null  by calling one of the handy methods in Optional

User · Answer

You also can use StringUtils isNoneEmpty     for check is null or empty

User · Answer

The last and the best one  i e   LOGICAL AND    if  foo    null  amp  amp  foo bar          etc        Because in logical  amp  amp        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

User · Answer

I would say method 4 is the most general idiom from the code that I ve looked at  But this always feels a bit smelly to me  It assumes foo    null is the same as foo bar      false    That doesn t always feel right to me

[java] Best way to check for null values in Java?

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