[java] Check if null Boolean is true results in exception

I have the following code:

Boolean bool = null;

try 
{
    if (bool)
    {
        //DoSomething
    }                   
} 
catch (Exception e) 
{
    System.out.println(e.getMessage());             
}

Why does my check up on the Boolean variable "bool" result in an exception? Shouldn't it just jump right past the if statement when it "sees" that it isn't true? When I remove the if statement or check up on if it's NOT null, the exception goes away.

as your variable bool is pointing to a null, you will always get a NullPointerException, you need to initialize the variable first somewhere with a not null value, and then modify it.

Boolean is the object wrapper class for the primitive boolean. This class, as any class, can indeed be null. For performance and memory reasons it is always best to use the primitive.

The wrapper classes in the Java API serve two primary purposes:

1. To provide a mechanism to “wrap” primitive values in an object so that the primitives can be included in activities reserved for objects, like as being added to Collections, or returned from a method with an object return value.
2. To provide an assortment of utility functions for primitives. Most of these functions are related to various conversions: converting primitives to and from String objects, and converting primitives and String objects to and from different bases (or radix), such as binary, octal, and hexadecimal.

http://en.wikipedia.org/wiki/Primitive_wrapper_class

Use the Apache BooleanUtils.

(If peak performance is the most important priority in your project then look at one of the other answers for a native solution that doesn't require including an external library.)

Don't reinvent the wheel. Leverage what's already been built and use isTrue():

BooleanUtils.isTrue( bool );

Checks if a Boolean value is true, handling null by returning false.

If you're not limited to the libraries you're "allowed" to include, there are a bunch of great helper functions for all sorts of use-cases, including Booleans and Strings. I suggest you peruse the various Apache libraries and see what they already offer.

Boolean types can be null. You need to do a null check as you have set it to null.

if (bool != null && bool)
{
  //DoSomething
}                   

Or with the power of Java 8 Optional, you also can do such trick:

Optional.ofNullable(boolValue).orElse(false)

:)

If you don't like extra null checks:

if (Boolean.TRUE.equals(value)) {...}