Differences among various bool types?

boolean is a java primitive type. It only accepts true or false (which are declared constants in java).

Boolean is a Serializable wrapper of boolean primitive type. From the JDK....

The Boolean class wraps a value of the primitive type boolean in an object. An object of type Boolean contains a single field whose type is boolean.

bool doesn't exist in java, but it does in Android as R.bool.

bool does not seem to exist, at least I can't find references to it.

boolean is a primitive boolean type, not an object.

Boolean is the wrapper object for a boolean.