\u00a7OO<\/p>\n
\u2022overriding methods can not have more restrictive access modifier
\n\u2022overriding methods can throw narrower or fewer exceptions<\/p>\n
\u2022overloaded methods can change return typs
\n\u2022overridding methods can not<\/p>\n
\u2022constructors
\n-this(): invoke constructor
\n-first line in constructor must be super() or this(), otherwise compiler will add them for you.<\/p>\n
\u00a7Garbagg collection
\n\u2022An object is eligible for garbage collection when no live thread can access it.<\/p>\n
\u2022Make object eligible for gc
\n-assign null to an object ref var
\n-assign object ref var to another obj<\/p>\n
\u2022Islands of isolation<\/p>\n
\u2022Request GC
\n-System.gc();
\n-Runtime rt = Runtime.getRuntim();
\nrt.gc();<\/p>\n
\u2022Java 2 Reference
\n-Strong ref: can not be gced
\n-Soft ref: gced when mem is low
\n-Weak ref: gced in next gc cycle
\n-Phantom ref: finalized but not gced<\/p>\n
\u00a7Inner Classes<\/p>\n
\u2022Instantiating inner class
\n-From within outer class
\nMyInner mi = new MyInner();
\n-From outside ths outer class
\nMyOuter.MyInner inner = new MyOuter().new MyInner();<\/p>\n
\u2022reference inner class instance within
\ninner class code
\n-this
\n\u2022reference outer this from within inner class code
\n-MyOuter.this<\/p>\n
\u2022Method-Local inner class
\n-can only be used below class def
\n-can not use local method var unless it’s final<\/p>\n
\u2022Anonymous Inner Class
\n-to override one or more methods of superclass
\n-ends with };
\n-new methods within anonymous inner class can’t be seen outside<\/p>\n
\u2022Argument-Defined Anonymous inner class<\/p>\n
\u2022static nested class
\nMyOuter.Nested n = new MyOuter.Nested();<\/p>\n
\u00a7Thread<\/p>\n
\u2022Two ways to create new threads
\n-extend Thread class
\n-implement Runnable<\/p>\n
\u2022Starting a thread
\nRunnable r = new MyRunnable();
\nThread t = new Thread(r);
\nt.start();<\/p>\n
\u2022Thread name
\nThread.currentThread().getName();<\/p>\n
\u2022dead thread can never be started again<\/p>\n
\u2022Thread states
\n-new
\n-runnable
\n-waiting\/blocked\/sleeping
\n-dead<\/p>\n
-sleep()
\n-yield()
\n-join()
\nThread t = new Thread();
\nt.start();
\nt.join();
\ncauses current thread to stop until thread t is dead<\/p>\n
\u2022synchronization
\n-only methods can be synchronized
\n-variables can not be synchronized
\n-each obj has one and only one lock
\n-if a thread goes to sleep, it takes locks with it
\n-a thread can acquire > 1 locks
\n-ok to have synchronized blocks and synchronize on diff objects<\/p>\n
\u2022Thread interaction
\n-wait(), notify(), notifyAll() must be called from within a synchronized context! A thread can’t invoke a wait or notify method on an object unless it owns that object’s lock
\n-use notifyAll()<\/p>\n","protected":false},"excerpt":{"rendered":"
\u00a7OO \u2022overriding methods can not have more restrictive access modifier \u2022overriding methods can throw narrower or fewer exceptions \u2022overloaded methods can change return typs \u2022overridding methods can not \u2022constructors -this(): invoke constructor -first line in constructor must be super() or … Continue reading