Best practice to validate null and empty collection in Java

Question

I want to verify whether a collection is empty and null  Could anyone please let me know the best practice   Currently  I am checking as below   if  null    sampleMap    sampleMap isEmpty           do something    else        do something else

User · Answer

You can use org apache commons lang Validate s  notEmpty  method   Validate notEmpty myCollection  -  Validate that the specified argument collection is neither null nor a size of zero  no elements   otherwise throwing an exception

User · Answer

If you use Spring frameworks  then you can use CollectionUtils to check against both Collections  List  Array  and Map etc   if CollectionUtils isEmpty

User · Answer

Personally  I prefer to use empty collections instead of null and have the algorithms work in a way that for the algorithm it does not matter if the collection is empty or not

User · Answer

That is the best way to check it  You could write a helper method to do it   public static boolean isNullOrEmpty  final Collection lt     gt  c         return c    null    c isEmpty       public static boolean isNullOrEmpty  final Map lt        gt  m         return m    null    m isEmpty

User · Answer

We ll check a Collection object is empty  null or not  these all methods which are given below  are present in org apache commons collections4 CollectionUtils package   Check on List or set type of collection Objects   CollectionUtils isEmpty listObject   CollectionUtils isNotEmpty listObject     Check on Map type of Objects   MapUtils isEmpty mapObject   MapUtils isNotEmpty mapObject     The return type of all methods is boolean

User · Answer

If you need to check for null  that is the way  However  if you have control on this  just return empty collection  whenever you can  and check only for empty later on   This thread is about the same thing with C   but the principles applies equally well to java  Like mentioned there  null should be returned only if        null might mean something more specific    your API  contract  might force you to return null

User · Answer

For all the collections including map use  isEmpty method which is there on these collection objects  But you have to do a null check before   Map lt String  String gt  map            if map  null  amp  amp   map isEmpty

User · Answer

When you use spring then you can use  boolean isNullOrEmpty   org springframework util ObjectUtils isEmpty obj     where obj is any  map collection array aything      otherwise  the code is   public static boolean isEmpty Object   array        return  array    null    array length    0      public static boolean isEmpty Object obj        if  obj    null            return true             if  obj getClass   isArray              return Array getLength obj     0            if  obj instanceof CharSequence            return   CharSequence  obj  length      0            if  obj instanceof Collection            return   Collection  obj  isEmpty              if  obj instanceof Map            return   Map  obj  isEmpty                  else     return false      for String best is   boolean isNullOrEmpty    str  null    str trim   isEmpty

User · Answer

If you use the Apache Commons Collections library in your project  you may use the CollectionUtils isEmpty and MapUtils isEmpty   methods which respectively check if a collection or a map is empty or null  i e  they are  null-safe     The code behind these methods is more or less what user  icza has written in his answer   Regardless of what you do  remember that the less code you write  the less code you need to test as the complexity of your code decreases

[java] Best practice to validate null and empty collection in Java

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