8/18/2019 SCJP chapter 2
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1.why inheritance : reuse,polymorphism
2. promote good oo cause you don't have one class that does
gazillion diff things
3.is a : extends imlements
4.has a : reference
.!ava does not have multiple inheritance coz deadly diamond of
death
".polymorphic invocations aply only to instance methods not
static
#.you extend a class then you can override all methods except
final
$.!vm uses virtual method invocation to dynamically select the
actual version of the method that
will run
%.overriding : argument match,return type match or su&
type,access level less restrictive,can
thow uncheced &ut not checed unless they are su&
types,()* +-/ *)--/0- -0/0- exceptions ie can tae less riss,can't
override static methods &ut they can &e redefined.
1.if you wnat to call super class's method instead of overriden
method then use super
super.callethod56
11.even though at runtime the overriden method is called at
compile time the compiler assumesthat you are calling super class's
method.
so there is a pro&lem at compile time if your super class
method declares an exception and thesu&class does not
12.overloaded methods: must change argument list,return
type,access,excepptions can change
13.which overriden method is called is decided at runtime &y
looing at o&!ect,which overloaded
method to call is decided at compile time &y looing at the
ref type.
14.so polymorphism does come into pplay only for overriden
methods.
1.you have )nimal a 7new 8og56
cool you can achieve polymorphism &ut what if u want to call
dog's emthod
you cast a to 8og.
compiler trusts us when we do
8og d 7 8og5a6
