How to check if an int is a null

An int is not null, it may be 0 if not initialized.

If you want an integer to be able to be null, you need to use Integer instead of int.

Integer id;
String name;

public Integer getId() { return id; }

Besides the statement if(person.equals(null)) can't be true, because if person is null, then a NullPointerException will be thrown. So the correct expression is if (person == null)

primitives dont have null value. default have for an int is 0.

if(person.getId()==0){}

Default values for primitives in java:

Data Type   Default Value (for fields)

byte                0
short               0
int                 0
long            0L
float           0.0f
double          0.0d
char            '\u0000'
boolean         false

Objects have null as default value.

String (or any object)--->null

1.) I need to check if the object is not null; Is the following expression correct;

if (person == null){
}

the above piece of code checks if person is null. you need to do

if (person != null){ // checks if person is not null
}

and

if(person.equals(null))

The above code would throw NullPointerException when person is null.

A primitive int cannot be null. If you need null, use Integer instead.