How to write nullable int in java?

Question

I want to convert a web form to a model in Java.

In C# I can write this:

<input name="id" value="" type="text"/>


public class Test
{
    public int? Id{get;set;}
}

The id can be null.

But in Java when using struts2 it throws an exception:

Method "setId" failed

So how to write this case in Java?

Possible dupes: http://stackoverflow.com/q/985151/1015495 http://stackoverflow.com/q/1123544/1015495 — Mike G, Jan 14 '13 at 15:19

score 162 · Accepted Answer · edited Sep 26 '19 at 15:40

162

Instead of using int you can use Integer (Integer javadoc) because it is a nullable Java class.

edited Sep 26 '19 at 15:40

Brent Matzelle

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answered Jan 14 '13 at 15:18

Ivaylo Strandjev

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thanks~ 'int' is same as 'Integer' in C#,so I didn't know this solution. – Dozer Jan 14 '13 at 15:21
@Dozer don't forget to mark this post as an answer once the 15 mins have past. – Luiggi Mendoza Jan 14 '13 at 15:24

Matthias Meid · Answer 2 · 2015-11-23T22:03:54.753

51

You can use an Integer, which is a reference type (class)in Java and therefore nullable.

Int32 (or int) is a struct (value type) in C#. In contrast, Integer in Java is a class which wraps an int. Instances of reference types can be null, which makes Integer an legit option.

Nullable<T> in .NET gives you similar options because it enables you to treat a value type like a nullable type. However, it's still different from Java's Integer since it's implemented as a struct (value type) which can be compared to null, but cannot actually hold a genuine null reference.

edited Nov 23 '15 at 22:03

answered Jan 14 '13 at 15:18

Matthias Meid

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this is a more thorough answer than the accepted one – John Demetriou Nov 23 '15 at 14:58

score 8 · Answer 3 · answered Jan 14 '13 at 15:18

8

In Java, just use Integer instead of int. This is essentially a nullable int. I'm not too familiar with Struts, but using Integer should allow you to omit the value.

answered Jan 14 '13 at 15:18

DigitalZebra

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score 1 · Answer 4 · answered Feb 12 '23 at 08:15

Optional<Integer> - The purpose of the class is to provide a type-level solution for representing optional values instead of null references.

OptionalInt - A container object which may or may not contain a int value. If a value is present, isPresent() will return true and getAsInt() will return the value.

How to write nullable int in java?

4 Answers4

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