OCAJP

OCAJP

1. break/continue

   • labeled
     • work as a go to statement
   • continue
     • only in loops
   • break
     • loop and switch

2. exceptions

   • printing
     • Stack
       • e.printStackTrace
     • default prints only name and message

3. conversions

   • narrowing
     • do not apply to
       • long
       • float
       • double
     • larger -> smaller datatype
     • auto casting
       • Accepts only constants of type int, short and byte for direct assign
   • widening
     • smaller -> larger datatype

4. Objects

   • pass by reference
     • pass the memory location
     • any changes to the object will affect other objects pointing to that memory location
     • assign to other object only changes the object memory location
       • other objects are not affected
   • Wrapper
     • immutables
       • Interger++ results in a new object with the new value

5. Inheritance

   • default or empty constructor will make JVM add a super() call

6. package modifier

   • public>protected>default>private

7. O.O.

   • Override
     • determined in run time what method is called
     • Covariant returns are allowed
       • subclasses as return type
   • Overload
     • determined in compile time what method is called

8. Strings/Wrappers

   • evaluated before operations
   • substring or anymethod that uses index goes from excluding the end index.

9. JAVA API

   • Math.round
     • positive
       • >= 0.5 gets the next positive number
     • negative
       • >= -0.6 gets the nect negative number

10. operator precedence

    • = has a low precedence
      • b1 != b2 = b1 results in compile error, because false = b1