The following are simple expressions of type `boolean`:

- The
*constants*`true`,`false`; *Variables*declared of type`boolean`;*Comparison operators*applied to primitive data types:`==`,`!=`,`>`,`<`,`>=`,`<=`*Calls to predicates*(i.e., methods that return a value of type`boolean`).

Complex expressions can be constructed from simple boolean expressions using
the boolean operators `!`, `&&`, and `||`. For such
operators, the following precedences hold:

`!``&&``||`

*Example:* The following is a correct expression of type `boolean`:

It is equivalent to:a || ! b && c

a || ((! b) && c)