Embracing Null-Handling in Conditions

You can avoid many extra lines of code by understanding how conditional statements behave with null values. If a variable someFlag is a Boolean variable that might be null, then the following conditional block executes only if someFlag is true.

A String variable can be null, an empty string (""), or can contain at least one character in it. If a variable middleName is a String, then the following conditional block executes only if middleName is not null and contains at least one character:

// If customer has a middle name...
if (middleName) {
  // Do something here if middleName has at least one character in it
}

If a variable recentOrders is a List, then the following conditional block executes only if recentOrders is not null and contains at least one element:

// If customer has any recent orders...
if (recentOrders) {
  // Do something here if recentOrders has at least one element
}

If a variable recentTransactions is a Map, then the following conditional block executes only if recentTransactions is not null and contains at least one map entry:

// If supplier has any recent transactions...
if (recentTransactions) {
  // Do something here if recentTransactions has at least one map entry
}

If a variable customerId can be null, and its data type is anything other than the ones described above then the following conditional block executes only if customerId has a non-null value:

// If non-boolean customerId has a value...
if (customerId) {
  // Do something here if customerId has a non-null value
}

If you need to test a Map entry in a conditional and there's a chance the Map might be null, then remember to use the safe-navigation operator (?.) when referencing the map key by name:

// Use the safe-navigation operator in case options Map is null
if (options?.orderBy) {
  // Do something here if the 'orderBy' key exists and has a non-null value
}