CPSC 233 TutorialXin Feb 7, 2011

James Tam

Assignment 3•Due on Friday, Feb 18

•Garbage collection•Runtime object•Array•Linked list/chain

Garbage collector In Foo f = new Foo();, f is a “reference” to the object If later you write f = new Foo(); or f = null; the

previously created object is not referenced any more It becomes a garbage Java will use a collector to free the memory occupied

by garbage When a garbage is freed, a finalize method is called

if you implement it for the class finalize() is used to free resources, such as files and

network connections

Runtime An object allows an application to interface

with the running environment getRuntime()

return the current runtime. gc()

Run the garbage collector. runFinalization()

Runs the finalization methods of any objects pending finalization.

Runtime -- exampleclass Runtime_foo{ public void finalize () { System.out.println("going"); }}

class Runtime_driver{ public static void main (String [] args) { Runtime_foo f = new Runtime_foo (); f = null; Runtime rt = Runtime.getRuntime(); rt.gc(); // calls finalize rt.runFinalization(); }}

Array A structure with a fixed number of elements int [] arr = new int[10]; arr[0] = 100;

Array – an examplepublic class StringArray{ public static void main (String [] args) {

String [] myStringArray = { "zero", "one", "two", "three", "four", "five", "six",

"seven", "eight", "nine"};

for (int i = 0; i < myStringArray.length; i++){ System.out.println(myStringArray[i]);}

}}

James Tam

List Elements: Nodes

Node

Data (data)Pointer/reference

(connector)

Data Ptr Data Ptr Data Ptr

Head

James Tam

List Operations: Linked Lists (Insertion)

•Graphical illustration of the algorithm:

NULL

LIST

NEW ELEMENT

Temp

James Tam

List Operations: Linked Lists (Insertion: 2)

•Graphical illustration of the algorithm:

NULL

LIST

NEW ELEMENT

Temp

James Tam

List Operations: Linked Lists (Insertion: 3)

•Graphical illustration of the algorithm:

NULL

LIST

NEW ELEMENT

Temp

James Tam

List Operations: Linked Lists (Removing Elements)

•Graphical illustration of the algorithm

NULL

LIST Remove

James Tam

List Operations: Linked Lists (Removing Elements: 2)

•Graphical illustration of the algorithm

NULL

LIST Remove

CurrentPrevious

James Tam

List Operations: Linked Lists (Removing Elements: 2)

•Graphical illustration of the algorithm

NULL

LIST Remove

CurrentPrevious

Node to be removed has been bypassed (effectively deleted from the list)

James Tam

Example -- Book Inventory

•UML