Null boolean

SLaks SLaks k gold badges silver badges bronze badges. So, bool? GetValueOrDefault ;. SteveC Joel Briggs Joel Briggs 1, 2 2 gold badges 12 12 silver badges 17 17 bronze badges. I think this is the best hybrid between conciseness and C noob-friendliness. Also note that there is an overload where you can specify the default value.

I like using this method, because it can create 'elegant' if statements if nullableBool. Value ;. David Yaw David Yaw The easiest way is to use the null coalescing operator:?? JaredPar JaredPar k gold badges silver badges bronze badges. If you want to test a condition, you can use this bool?

You can also use this to assign a regular bool from a bool? The complete way would be: bool b1; bool? CodeNaked CodeNaked Something like: if bn. Sign up or log in Sign up using Google. Use boolean rather than Boolean every time you can.

This will avoid many NullPointerException s and make your code more robust. I almost never use Boolean because its semantics are vague and obscure. Basically you have 3-state logic: true, false or unknown. Sometimes it is useful to use it when e. I see no reason to convert from boolean to Boolean as it introduces extra memory overhead, NPE possibility and less typing.

Typically I use awkward BooleanUtils. The only reason for the existence of Boolean is the ability to have collections of Boolean type generics do not allow boolean , as well as all other primitives. The Boolean class is a wrapper around the boolean primitive type. The use of this wrapper is to be able to pass a boolean in a method that accepts an object or generic.

Ie vector. If your reference to a Boolean is null, it simply means that your Boolean was never created. A null Boolean reference should only be used to trigger similar logic to which you have any other null reference. Using it for three state logic is clumsy. EDIT2: Please read comments below. If anyone has an idea of how to restructure my answer to incorporate this, please do so. This answer is intended to help those - like me - who do not have a complete understanding of the issues.

If I use incorrect language please correct me. The syntax for Boolean is abbreviated and conceals the fact that the reference points to Objects:. If an object it is necessary to test for null to avoid NPE.

For me it is psychologically easier to remember this if there is an equality test:. So the shortened form is only safe when a is a primitive. Wrapper classes for primitives can be used where objects are required, collections are a good sample. Imagine you need for some reason store a sequence of boolean in an ArrayList , this can be done by boxing boolean in Boolean. There is a few words about this here. Collections can only hold object references, so you have to box primitive values into the appropriate wrapper class which is Integer in the case of int.

When you take the object out of the collection, you get the Integer that you put in; if you need an int, you must unbox the Integer using the intValue method. All of this boxing and unboxing is a pain, and clutters up your code. The autoboxing and unboxing feature automates the process, eliminating the pain and the clutter.

Boolean wrapper is useful when you want to whether value was assigned or not apart from true and false. It has the following three states:. The above difference will make it helpful in Lists of Boolean values, which can have True , False or Null.

I suppose in some case, you should have a mechanism to distinguish a Boolean field which already set value or not.

Main purpose for Boolean is null value. Null value says, that property is undefined , for example take database nullable column. If you really need to convert everyting from primitive boolean to wrapper Boolean, then you could use following to support old code:. For example, you may have in a form a field named "newsletter" that indicate if the user want or doesn't want a newsletter from your site. If the user doesn't select a value in this field, you may want to implement a default behaviour to that situation send?

In a strict definition of a boolean element, there are only two values. In a perfect world, that would be true. In the real world, the element may be missing or unknown. Typically, this involves user input. In a screen based system, it could be forced by an edit. In a batch world using either a database or XML input, the element could easily be missing. So, in the non-perfect world we live in, the Boolean object is great in that it can represent the missing or unknown state as null.

After all, computers just model the real world an should account for all possible states and handle them with throwing exceptions mostly since there are use cases where throwing the exception would be the correct response. You do this by setting the variable or property to Nothing , as the following example shows. Although you can assign Nothing to a variable of a nullable value type, you cannot test it for Nothing by using the equal sign.

To retrieve the value of a variable of a nullable value type, you should first test its HasValue property to confirm that it has a value. The following example shows the recommended way to read the variable numberOfChildren of the previous examples. When nullable Boolean variables are used in Boolean expressions, the result can be True , False , or Nothing.

The following is the truth table for And and Or. Because b1 and b2 now have three possible values, there are nine combinations to evaluate. When the value of a Boolean variable or expression is Nothing , it is neither true nor false. Consider the following example. In this example, b1 And b2 evaluates to Nothing. As a result, the Else clause is executed in each If statement, and the output is as follows:. AndAlso and OrElse , which use short-circuit evaluation, must evaluate their second operands when the first evaluates to Nothing.

If one or both of the operands of an arithmetic, comparison, shift, or type operation is a nullable value type, the result of the operation is also a nullable value type.

If both operands have values that are not Nothing , the operation is performed on the underlying values of the operands, as if neither were a nullable value type. In the following example, variables compare1 and sum1 are implicitly typed.

I receive from an object entity a field that mus be Boolean because it is entity and null is of course false. So i think the best answer is just to compare it to Boolean.

Add a comment. Active Oldest Votes. Try that approach: Boolean. Improve this answer. Radoslav Ivanov Radoslav Ivanov 6 6 silver badges 19 19 bronze badges. OP might want the null. The question says into Boolean not boolean , still useful for others that just need the primitive — StevenWernerCS. String BooleanUtils. Chet Chet You can compare it to Boolean. TRUE or Boolean.