How to Properly Check for Null Values in a Double Variable?

How can I check if a double variable in Java is null when querying a database?

if (results == null) {
     results = 0;
}

In Java, primitive types such as `double` cannot hold a `null` value. Therefore, when you define a variable of type `double`, it default initializes to `0.0`. To handle potential null results from a database query, it is essential to use the corresponding wrapper class, `Double`, which can be assigned a null value.

Double results = null; // Allow results to be null

if (results == null) {
    results = 0.0; // Initialize to zero if null
} else {
    // Further processing with results
}

Causes

• Using a primitive data type `double` which cannot be null.
• Expecting the `== null` comparison to work with primitives.

Solutions

• Change the data type from `double` to `Double` to allow null values.
• Check if the `Double` variable is null before performing any operations.

Mistake: Trying to compare a primitive type with null using `==`.

Solution: Ensure you use the wrapper `Double` class instead of the primitive type.

Mistake: Assuming primitive double can be null and writing logic based on that.

Solution: Always use `Double` for nullable scenarios when dealing with databases.