5.1.7 Forbidden Conversions

• There is no permitted conversion from any reference type to any primitive type.
• Except for the string conversions, there is no permitted conversion from any primitive type to any reference type.
• There is no permitted conversion from the null type to any primitive type.
• There is no permitted conversion to the null type other than the identity conversion.
• There is no permitted conversion to the type boolean other than the identity conversion.
• There is no permitted conversion from the type boolean other than the identity conversion and string conversion.
• There is no permitted conversion other than string conversion from class type S to a different class type T if S is not a subclass of T and T is not a subclass of S.
• There is no permitted conversion from class type S to interface type K if S is final and does not implement K.
• There is no permitted conversion from class type S to any array type if S is not Object.
• There is no permitted conversion other than string conversion from interface type J to class type T if T is final and does not implement J.
• There is no permitted conversion from interface type J to interface type K if J and K declare methods with the same signature but different return types.
• There is no permitted conversion from any array type to any class type other than Object or String.
• There is no permitted conversion from any array type to any interface type, except to the interface type Cloneable, which is implemented by all arrays.
• There is no permitted conversion from array type SC[] to array type TC[] if there is no permitted conversion other than a string conversion from SC to TC.