boolean is akeyword which designates thebooleanprimitive type. There are only two possibleboolean values:true andfalse. The default value forboolean fields isfalse.
The following is a declaration of aprivateboolean field namedinitialized, and its use in a method namedsynchronizeConnection.
 | Code section 1: Connection synchronization.privatebooleaninitialized=false;publicvoidsynchronizeConnection(){if(!initialized){connection=connect();initialized=true;}} |
The previous code only creates a connection once (at the first method call). Note that there is no automatic conversion between integer types (such asint) toboolean as is possible in some languages likeC. Instead, one must use an equivalent expression such as(i != 0) which evaluates totrue ifi is not zero.