How to check if an int is a 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.
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)
A primitive int
cannot be null. If you need null, use Integer
instead.