Question

I have an object called Person.

it has several attributes in it;

int id;
String name;

i set a person object like Person p = new Person(1,"Joe");.

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

if (person == null){
}

Or


if(person.equals(null))

2.) I need to know if the ID contains an Int.

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

But, java doesn’t allow it. How can i do this check ?

Answer 1

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)