How to write nullable int in java?

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.

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.

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