Literals

Literals in expressions are literal values that can be:

A number.
A string (can be enclosed in double ("") or single ('') quotation marks).
A character (any one-character string).
The JADE-defined (that is, system-defined) Boolean literals:
- true
- false
Use these true and false system-defined Boolean literal values to initialize a Boolean variable.
The JADE-defined null literal, which represents the null, or uninitialized, state of primitive type values or object references. Use the system-defined null literal to initialize an object reference or compare for an empty object, as shown in the code fragments in the following examples.
```
if customer <> null then
    customer.name := "John Doe";
endif;

if customer = null then
    write "Uninitialized customer";
else
    write customer.name;
endif;
```