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