Boxed Boolean values should not be used in conditional expressions JAVA-E1054

A boxed boolean value (java.lang.Boolean) is being used in a potentially dangerous manner. Such usage may lead to a NullPointerException being thrown.

Java's primitive types differ from normal classes in that primitives can never be null. However, classes can be null, even primitive wrapper classes such as Boolean or Character. For Boolean in particular, this means that turning a boolean into a Boolean promotes it from a binary true or false to a ternary true, false or null. This may be undesirable in most cases, and is worth avoiding.

The nullability of wrapper types becomes an issue when the wrapper types are used directly in expressions without null checks.

Bad Practice

In the example below, the if statement evaluates the value of nullable when its value is null. This will lead to a NullPointerException being thrown.

Boolean nullable = null

if (nullable) { // This would throw a NullPointerException.
    // ...
}

Recommended

You could perform an explicit comparison with the required value.

if (nullable == true) {
    // ...
}

// OR

if (Boolean.TRUE.equals(nullable)) {
    // ...
}

Using Boolean.TRUE here can prevent an unnecessary unboxing conversion when performing a comparison.