Can an Int Be Null in Java

Can an int be null in Java?

int can't be null, but Integer can. You need to be careful when unboxing null Integers since this can cause a lot of confusion and head scratching!

e.g. this:

int a = object.getA(); // getA returns a null Integer

will give you a NullPointerException, despite object not being null!

To follow up on your question, if you want to indicate the absence of a value, I would investigate java.util.Optional<Integer>

why int can't be compared to null but Integer can be compared to null

int a,b,c;
if (a == null) {
    //code here
}

This code doesn't make sense, because primitive int types cannot be null. Even if you considered auto-boxing, int a is guaranteed to have a value before being boxed.

Integer a,b,c;
if (a == null) {
   //code here
}

This code makes sense, because Object Integer types can be null (no value).

As far as the functionality, the Object vs built-in types actually do make a bit of a difference (due to their different natures).

Integer a,b,c;
if (a == b) {
  // a and b refer to the same instance.
  // for small integers where a and b are constructed with the same values,
  // the JVM uses a factory and this will mostly work
  //
  // for large integers where a and b are constructed with the same values,
  // you could get a == b to fail
}

while

int a,b,c;
if (a == b) {
  // for all integers were a and b contain the same value,
  // this will always work
}

How to set to int value null? Java Android

In this case, I would avoid using null all together.

Just use -1 as your null

If you need -1 to be an acceptable (not null) value, then use a float instead. Since all your real answers are going to be integers, make your null 0.1

Or, find a value that the x will never be, like Integer.MAX_VALUE or something.

Can not set int field to null value

The primitive datatype int isn't nullable. You need to use the Wrapper class Integer in this case. So just replace the type.

Setting null value to integer

I am sure you are over-complicating the problem, it is a real simple thing to do. Check the code below:

Integer i = null;
System.out.println(i == null ?"":i);

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)

How to assign a null value to a single element in an int[] array in Java

Primitive Java integers cannot be null, but the Integer class, which wraps a primitive int can be null. Here is one option to consider:

Integer[] num = new Integer[3];
num[0] = 23;
num[1] = null;
num[2] = 12;

The boxing rules in Java make it fairly easy to use int and Integer interchangeably, most of the time.

How to accept an empty integer value?

Change your variable types to the wrapper classes(Integer, Double) of primitive types(int, double). In Java, primitive types cannot be null.

How to check whether an Integer is null or zero in Java?

Since StringUtils class is mentioned in the question, I assume that Apache Commons lib is already used in the project.

Then you can use the following:

if (0 != ObjectUtils.defaultIfNull(myInteger, 0)) { ... }

Or using static import:

if (0 != defaultIfNull(myInteger, 0)) { ... }

---

Related Topics