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.

Solution 1:

If you don't like extra null checks:

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

Solution 2:

When you have a boolean it can be either true or false. Yet when you have a Boolean it can be either Boolean.TRUE, Boolean.FALSE or null as any other object.

In your particular case, your Boolean is null and the if statement triggers an implicit conversion to boolean that produces the NullPointerException. You may need instead:

if(bool != null && bool) { ... }

Solution 3:

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.

Solution 4:

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

Optional.ofNullable(boolValue).orElse(false)

:)

Solution 5:

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

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