I have two scenarios given below.
Case1:
if( folderProcessChecklistBean.getFolderProcessChecklistRecord() .getChecklistCode() != null) Case2:
if(!folderProcessChecklistBean.getFolderProcessChecklistRecord() .getChecklistCode().equals(null)) Can anyone tell me if both approaches are the same or not?
You can never call the .equals() method on an object reference that is null. It is a method, just like the rest, so if the object reference is truly null it will just throw a NullPointerException.
If you want to check if a reference is not pointing to any object, i.e. it is a null reference you must use the ==.
The equals() method on the other hand is used if you want to compare the data contained in the object. If the class in question overrides the equals(), like for example String does, then it will compare the contents of the object, rather than just whether it is the same object reference.
If you see an object like a box. == is comparing whether it is the same box while equals() compares the contents of two boxes.
You should always use
myObject != null because if myObject is null
!myObject.equals(null); // <- Exception! null.equals(...); doesn't work! myObject != null; // <- Quite OK Case 2 will not work. If the result you want to compare is null, the call of the equals(Object) method will raise a NullPointerException. So you have to use case 1.
The results will be the same if Object returned by getChecklistCode() implements equals according to Object.equals contract which says x.equals(null) should return false
You can get an exception if you use Case2
If folderProcessChecklistBean.getFolderProcessChecklistRecord().getChecklistCode() return null, then it'll throw an exception to use equals.
<Object> obj = folderProcessChecklistBean.getFolderProcessChecklistRecord().getChecklistCode(); if (obj!=null){...} == operator is used to compare 2 objects reference equality
equals() check the value of the objects are same
Case 1
if( folderProcessChecklistBean.getFolderProcessChecklistRecord() .getChecklistCode() != null) it will check the object doesn't have any object reference assigned to it
case 2:
if(!folderProcessChecklistBean.getFolderProcessChecklistRecord() .getChecklistCode().equals(null)) equals is a method, if you try to invoke it on a null reference, it will Throws a NullPointerException, you can't dereference object, it doesn't refer to anything
== checks reference equality whereas .equals() check value equality. The reason why you should use reference equality is to avoid a NPE, as described in a few others above.
== check if two objects are the same, equals() compare two objects