Check object empty

Question

Basically how do you check if an object is null or empty   What I mean is that if I have an object instantiated but all its values or fields are null  the how do I check in code if it is empty   I have tried   if  doc    null        do something   But it doesn t seem to work

User · Answer

You should check it against null   If you want to check if object x is null or not  you can do       if x    null    But if it is not null  it can have properties which are null or empty  You will check those explicitly       if x getProperty      null    For  empty  check  it depends on what type is involved  For a Java String  you usually do       if str    null  amp  amp   str isEmpty      As you haven t mentioned about any specific problem with this  difficult to tell

User · Answer

I have a way  you guys tell me how good it is   Create a new object of the class and compare it with your object  which you want to check for emptiness    To be correctly able to do it    Override the hashCode   and equals   methods of your model class and also of the classes  objects of whose are members of your class  for example    Person class  primary model class     public class Person        private int age      private String firstName      private String lastName      private Address address         getters and setters       Override     public int hashCode             final int prime   31          int result   1          result   prime   result     address    null    0   address hashCode             result   prime   result   age          result   prime   result     firstName    null    0   firstName hashCode             result   prime   result     lastName    null    0   lastName hashCode             return result              Override     public boolean equals Object obj            if  this    obj              return true          if  obj    null              return false          if  getClass      obj getClass                return false          Person other    Person  obj          if  address    null                if  other address    null                  return false            else if   address equals other address               return false          if  age    other age              return false          if  firstName    null                if  other firstName    null                  return false            else if   firstName equals other firstName               return false          if  lastName    null                if  other lastName    null                  return false            else if   lastName equals other lastName               return false          return true              Override     public String toString             return  Person  age     age      firstName     firstName      lastName     lastName      address     address                                   Address class  used inside Person class     public class Address        private String line1      private String line2         getters and setters       Override     public int hashCode             final int prime   31          int result   1          result   prime   result     line1    null    0   line1 hashCode             result   prime   result     line2    null    0   line2 hashCode             return result              Override     public boolean equals Object obj            if  this    obj              return true          if  obj    null              return false          if  getClass      obj getClass                return false          Address other    Address  obj          if  line1    null                if  other line1    null                  return false            else if   line1 equals other line1               return false          if  line2    null                if  other line2    null                  return false            else if   line2 equals other line2               return false          return true              Override     public String toString             return  Address  line1     line1      line2     line2                     Now in the main class        Person person1   new Person        person1 setAge 20        Person person2   new Person         Person person3   new Person     if person1 equals person2   -- gt  this will be false  if person2 equals person3   -- gt  this will be true   I hope this is the best way instead of putting if conditions on each and every member variables   Let me know

User · Answer

I suggest you add separate overloaded method and add them to your projects Utility Utilities class      To check for Collection be empty or null   public static boolean isEmpty Collection obj        return obj    null    obj isEmpty        or use Apache Commons CollectionUtils isEmpty       To check if Map is empty or null   public static boolean isEmpty Map lt      gt  value        return value    null    value isEmpty        or use Apache Commons MapUtils isEmpty       To check for String empty or null   public static boolean isEmpty String string        return string    null    string trim   isEmpty        or use Apache Commons StringUtils isBlank    To check an object is null is easy but to verify if it s empty is tricky as object can have many private or inherited variables and nested objects which should all be empty  For that All need to be verified or some isEmpty   method be in all objects which would verify the objects emptiness

User · Answer

This can be done with java reflection This method returns false if any one attribute value is present for the object  hope it helps some one  public boolean isEmpty           for  Field field   this getClass   getDeclaredFields              try               field setAccessible true               if  field get this   null                    return false                          catch  Exception e              System out println  Exception occured in processing                        return true

User · Answer

If your Object contains Objects then check if they are null  if it have primitives check for their default values    for Instance   Person Object  name Property with getter and setter  to check if name is not initialized    Person p   new Person    if p getName    null

User · Answer

let suppose     data        if  if    isEmptyObject data           document write  Object is empty      else      document write  Object is not empty       It worked for me and its an easy way to check if object is empty or not

User · Answer

In Java  you can verify using Object utils    import static java util Objects isNull  if IsNull yourObject        your block here

User · Answer

You can t do it directly  you should provide your own way to check this  Eg   class MyClass     Object attr1  attr2  attr3     public boolean isValid         return attr1    null  amp  amp  attr2    null  amp  amp  attr3    null          Or make all fields final and initialize them in constructors so that you can be sure that everything is initialized

[java] Check object empty

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