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ArrayList of References / Objects – get,set,remove,add,size – levels of abstraction Matrix / 2 D Array – nested loops, GridWorld ( grid ) GridWorld or Make a Class – location, actor, bug, critter, grid, super, abstract String / Array Question – find biggest, find smallest, etc.

© A+ Computer Science - www.apluscompsci.com -Read all 4 questions before writing anything -answer the easiest question 1 st -most times question 1 is the easiest -see if part B calls part A and so on -many times part C consists of A and B calls -write something on every question -write legibly / use PENCIL!!!!!!!!!! -keep track of your time

© A+ Computer Science - www.apluscompsci.com -When writing methods -use parameter types and names as provided -do not redefine the parameters listed -do not redefine the methods provided -return from all return methods -return correct data type from return methods

© A+ Computer Science - www.apluscompsci.com -When writing a class or methods for a class -know which methods you have -know which instance variables you have -check for public/private on methods/variables -return from all return methods -return correct data type from return methods

© A+ Computer Science - www.apluscompsci.com -When extending a class -know which methods the parent contains -have the original class where you can see it -make sure you have super calls -check for public/private on methods/variables -make super calls in sub class methods as needed

© A+ Computer Science - www.apluscompsci.com -When extending abstract / implementing interface -know which methods the parent contains -have the original class where you can see it -make sure you have super calls -check for public/private on methods/variables -make super calls in sub class methods as needed -implement all abstract methods in sub class

© A+ Computer Science - www.apluscompsci.com -When writing GridWorld question -use the GridWorld quick reference -use original method code when overidding -use Bug and BoxBug code if extending Bug -use Critter and ChameleonCritter code if extending Critter -use Critter and Bug for extends demo -use Critter for ArrayList and Math.random() demo -use GW quick reference on the entire AP test

© A+ Computer Science - www.apluscompsci.com ArrayList of References / Objects – get,set,remove,add,size – levels of abstraction Matrix / 2 D Array – nested loops, GridWorld ( grid ) GridWorld or Make a Class – location, actor, bug, critter, grid, super, abstract String / Array Question – find biggest, find smallest, etc.

© A+ Computer Science - www.apluscompsci.com 0 1 2 3 4 5 6 7 8 9 nums0000000000 int[] nums = new int[10]; //Java int array An array is a group of items all of the same type which are accessed through a single identifier.

© A+ Computer Science - www.apluscompsci.com ArrayList frequently used methods NameUse add(item)adds item to the end of the list add(spot,item)adds item at spot – shifts items up-> set(spot,item)put item at spot z[spot]=item get(spot)returns the item at spot return z[spot] size()returns the # of items in the list remove()removes an item from the list clear()removes all items from the list import java.util.ArrayList;

© A+ Computer Science - www.apluscompsci.com List ray = new ArrayList(); ray.add("hello"); ray.add("whoot"); ray.add("contests"); out.println(((String)ray.get(0)).charAt(0)); out.println(((String)ray.get(2)).charAt(0)); ray stores Object references. OUTPUT h c

© A+ Computer Science - www.apluscompsci.com List ray; ray = new ArrayList (); ray.add("hello"); ray.add("whoot"); ray.add("contests"); out.println(ray.get(0).charAt(0)); out.println(ray.get(2).charAt(0)); ray stores String references. OUTPUT h c

public void addClimb( String peakName, int climbTime ) { ClimbInfo c = new ClimbInfo( peakName, climbTime ); climbList.add( c ); } You must know ArrayList!

public void addClimb( String peakName, int climbTime ) { ClimbInfo c = new ClimbInfo( peakName, climbTime ); for( int i = 0; i < climbList.size(); i++ ) { int x = peakName.compareTo( climbList.get(i).getName() ); if( x <= 0 ) { climbList.add( i, c ); break; } } if( sz == climbList.size() ) climbList.add( c ); } You must know ArrayList!

NO YES You must know ArrayList!

© A+ Computer Science - www.apluscompsci.com Visit us at www.apluscompsci.com Full Curriculum Solutions www.apluscompsci.com M/C Review Question Banks Live Programming Problems Tons of great content! www.facebook.com/APlusComputerScience

© A+ Computer Science - www.apluscompsci.com One question on the A test free response will require that you create a class. Sometimes you have to extend an abstract class or implement an interface. Other times, you will extend another class like Critter.

© A+ Computer Science - www.apluscompsci.com Location frequently used methods NameUse Location(row, col)creates a new row,col Location getCol()gets the column value for this location getRow()gets the row value for this location getAdjacentLocation( x)get a loc adjacent to x getDirectionToward( x )get the dir to another actor import info.gridworld.grid.Location;

© A+ Computer Science - www.apluscompsci.com Location frequently used fields NameUse NORTHindicates going north – value of 0 SOUTHindicates going south – value of 180 EASTindicates going east – value of 90 WESTindicates going west – value of 270 import info.gridworld.grid.Location;

© A+ Computer Science - www.apluscompsci.com Location locOne = new Location(2,1); Location locTwo = new Location(1,3); out.println(locOne.getAdjacentLocation(Location.NORTH)); out.println(locOne.getAdjacentLocation(Location.SOUTH)); out.println(locOne.getAdjacentLocation(Location.EAST)); out.println(locOne.getAdjacentLocation(Location.WEST)); OUTPUT (1, 1) (3, 1) (2, 2) (2, 0) 0,00,10,20,30,4 1,01,11,21,31,4 2,02,12,22,32,4 3,03,13,23,33,4

© A+ Computer Science - www.apluscompsci.com Location locOne = new Location(2,1); Location locTwo = new Location(1,3); out.println(locOne.getDirectionToward(locTwo)); OUTPUT 45 0,00,10,20,30,4 1,01,11,21,31,4 2,02,12,22,32,4 3,03,13,23,33,4

© A+ Computer Science - www.apluscompsci.com Actor frequently used methods NameUse Actor()creates new blue north bound actor act()reverses the direction for actor getColor()gets the actor’s color getDirection()gets the actor’s direction getLocation()gets the actor’s location setColor(col)sets the actor’s color to col setDirection(dir)sets the actor’s direction to dir moveTo(loc)moves the actor to new location loc

© A+ Computer Science - www.apluscompsci.com Actor frequently used methods NameUse putSelfInGrid(grid, loc)put this actor in grid at loc removeSelfFromGrid()takes this actor out of the grid getGrid()gets the grid which contains this actor toString()gets actor data as a String import info.gridworld.actor.Actor;

© A+ Computer Science - www.apluscompsci.com ActorWorld world = new ActorWorld(); Actor dude = new Actor(); dude.setColor(Color.GREEN); dude.setDirection(Location.SOUTH); Location loc = new Location(2,2); world.add(loc, dude); world.show(); What happens if you click on an empty location?

© A+ Computer Science - www.apluscompsci.com Grid abstract methods NameUse get(loc)returns the ref at location loc getEmptyAdjacentLocations(loc)gets the valid empty locs in 8 dirs getNeighbors(loc)returns the objs around this getNumCols()gets the # of cols for this grid getNumRows()gets the # of rows for this grid getOccupiedAdjacentLocations(loc)gets the valid locs in 8 dirs that contain objs getOccupiedLocations()gets locs that contain live objs getValidAdjacentLocations(loc)gets the valid locs in 8 dirs isValid(loc)checks to see if loc is valid put(loc, obj)put the obj in grid at location loc remove(loc)take the obj at location loc out of the grid import info.gridworld.grid.Grid;

© A+ Computer Science - www.apluscompsci.com Grid is an interface that details the behaviors expected of a Grid. Grid was designed as an interface because many different structures could be used to store the grid values. An interface works perfectly due to the large number of unknowns.

© A+ Computer Science - www.apluscompsci.com Grid grd; grd = new BoundedGrid ( 4, 5 ); grd.put( new Location( 2, 2 ), "CAT" ); grd.put( new Location( 1, 3 ), "DOG" ); System.out.println( grd.get( new Location( 0, 0 ) ); System.out.println( grd.get( new Location( 2, 2 ) ); OUTPUT null CAT null DOGnull CATnull

© A+ Computer Science - www.apluscompsci.com Bug extends Actor frequently used methods NameUse act()move if possible or turn getColor()gets the bug’s color getDirection()gets the bug’s direction getLocation()gets the bug’s location setColor(col)sets the bug’s color to col setDirection(dir)sets the bug’s direction to dir import info.gridworld.actor.Bug;

© A+ Computer Science - www.apluscompsci.com Bug extends Actor frequently used methods – Bug only NameUse Bug()make a new red bug going north Bug(color)make a new color bug act()move if possible or turn canMove()check to see if a move is possible move()move forward and leave a flower turn()turn 45 degrees without moving import info.gridworld.actor.Bug;

© A+ Computer Science - www.apluscompsci.com ActorWorld world = new ActorWorld(); Bug dude = new Bug(); world.add(new Location(3,3), dude); Bug sally = new Bug(Color.GREEN); sally.setDirection(Location.SOUTHEAST); world.add(new Location(2,2), sally); Bug ali = new Bug(Color.ORANGE); ali.setDirection(Location.NORTHEAST); world.add(new Location(1,1), ali); world.show();

© A+ Computer Science - www.apluscompsci.com The bug act method looks to see if a move is possible by calling canMove. canMove looks at the location in front of this bug to see if it is empty or if it contains a flower. canMove returns true or false.

© A+ Computer Science - www.apluscompsci.com The bug act method calls move if canMove returns true. move calls moveTo to move the bug to the location in front of this bug. move leaves a flower in the old location.

© A+ Computer Science - www.apluscompsci.com Critter extends Actor frequently used methods NameUse getColor()gets the critter's color getDirection()gets the critter's direction getLocation()gets the critter's location setColor(col)sets the critter's color to col setDirection(dir)sets the critter's direction to dir import info.gridworld.actor.Critter;

© A+ Computer Science - www.apluscompsci.com Critter extends Actor frequently used methods – Critter specific NameUse act()calls the methods listed below getActors()gets all actors around this location processActors(actors)do something to actors sent in getMoveLocations()gets list of possible move locs selectMoveLocation(locs)picks loc to move to makeMove(loc)moves this critter to loc import info.gridworld.actor.Critter;

© A+ Computer Science - www.apluscompsci.com if no grid present – stop call getActors to get list of actors to proces processActors received from getActors call getMoveLocations to get a list of locations to which the critter might move call selectMoveLocation to select new location move to the new loc

© A+ Computer Science - www.apluscompsci.com The getActors method returns an ArrayList containing all of the actors around this critter using the 4 cardinal(N,S,E,W) and 4 intercardinal directions(NE, NW, SE, SW). In order to change which actors are returned by getActors, override the method and provide a different method of selecting actors. getActors must not modify any actors.

© A+ Computer Science - www.apluscompsci.com A typical Abstract/Interface question requires that a class be written that extends the abstract class or implements the interface and that all abstract method(s) be implemented.

© A+ Computer Science - www.apluscompsci.com abstract class Monster{ private String myName; public Monster() { myName =""; } public Monster(String name) { myName =name; } public String getName() { return myName; } public abstract void talk( ); public String toString() { return myName + "\n"; }

© A+ Computer Science - www.apluscompsci.com class Vampire extends Monster { public Vampire( String name ) { super(name); } public void talk() { out.println("Vampire " + getName() + " say \"I want to drink your blood!\""); }

© A+ Computer Science - www.apluscompsci.com public abstract class APlus { public APlus(int x) //constructor code not shown public abstract double goForIt(); //other fields/methods not shown } Pet Item

© A+ Computer Science - www.apluscompsci.com public class PassAPTest extends APlus { public PassAPTest(int x) { super(x); } public double goForIt() { double run=0.0; //write some code - run = x*y/z return run; } //other fields/methods not shown } public abstract class APlus { public APlus(int x) //constructor code not shown public abstract double goForIt(); //other fields/methods not shown }

© A+ Computer Science - www.apluscompsci.com public interface Exampleable { public abstract int writeIt(Object o); public static final int x = 123; } Methods are public abstract! Variables are public static final!

© A+ Computer Science - www.apluscompsci.com An interface is a list of abstract methods that must be implemented. An interface may not contain any implemented methods. Interfaces cannot have constructors!!!

© A+ Computer Science - www.apluscompsci.com Interfaces are typically used when you know what you want an Object to do, but do not know how it will be done. If only the behavior is known, use an interface.

© A+ Computer Science - www.apluscompsci.com Abstract classes are typically used when you know what you want an Object to do and have a bit of an idea how it will be done. If the behavior is known and some properties are known, use an abstract class.

public class RetroBug extends Bug { private Location savedLocation; private int savedDirection; public void act() { savedLocation = getLocation(); savedDirection = getDirection(); super.act(); } public void restore() { if( savedLocation == null ) return; setDirection( savedDirection ); if( getGrid().get(savedLocation) == null || getGrid().get(savedLocation) instanceof Flower ) { moveTo( savedLocation ); }

© A+ Computer Science - www.apluscompsci.com 0 1 2 3 4 5 6 7 8 9 nums0000000000 int[] nums = new int[10]; //Java int array An array is a group of items all of the same type which are accessed through a single identifier.

© A+ Computer Science - www.apluscompsci.com String frequently used methods NameUse substring(x,y)returns a section of the string from x to y not including y substring(x)returns a section of the string from x to length-1 length()returns the # of chars charAt(x)returns the char at spot x indexOf(c)returns the loc of char c in the string, searching from spot 0 to spot length-1 lastIndexOf(c)returns the loc of char c in the string, searching from spot length-1 to spot 0

© A+ Computer Science - www.apluscompsci.com String frequently used methods NameUse equals(s)checks if this string has same chars as s compareTo(s)compares this string and s for >,<, and == trim()removes leading and trailing whitespace replaceAll(x,y)returns a new String with all x changed to y toUpperCase()returns a new String with uppercase chars toLowerCase()returns a new String with lowercase chars

© A+ Computer Science - www.apluscompsci.com String sent = "alligators rule"; String find = "gato"; System.out.println( sent.indexOf( find ) ); System.out.println( sent.indexOf( "dog" ) ); System.out.println( sent.substring( 3, 6 ) ); System.out.println( sent.substring( 6 ) ); OUTPUT 4 -1 iga tors rule

public int findHorseSpace( String name ) { for( int i = 0; i < spaces.length; i++ ) { if( spaces[i] != null ) if(name.equals(spaces[i].getName()) return i; } return -1; }

public void consolidate( ) { Horse[] tmp = new Horse[ spaces.length ]; int loc = 0; for( Horse h : spaces) if( h != null ) { tmp[ loc ] = h; loc++; } spaces = tmp; }

© A+ Computer Science - www.apluscompsci.com int[][] mat = {{5,7,9,2,1,9}, {5,3,4}, {3,7,0,8,9}}; out.println(mat[2][1]); out.println(mat[1][2]); out.println(mat[0][3]); out.println(mat[2][4]); OUTPUT 7 4 2 9

© A+ Computer Science - www.apluscompsci.com int[][] mat = {{5,7,9,2,1,9}, {5,3,4}, {3,7,0,8,9}}; out.println(mat[7/4][0]); out.println(mat[1*2][2]); out.println(mat.length); out.println(mat[0].length); OUTPUT 5 0 3 6

© A+ Computer Science - www.apluscompsci.com //start //stop //increment for(outer=1; outer<=2; outer++) { } OUTPUT 1 1 2 //start //stop //increment for(int inner=1; inner<=2; inner++) out.println(outer + " " + inner); out.println(); OUTPUT 1 1 2 2 1 2 int outer=1;

© A+ Computer Science - www.apluscompsci.com int[] nums = {1,2,3,4,5,6,7}; for(int r=0; r<nums.length; r++) { out.println(nums[r]); } OUTPUT 1 2 3 4 5 6 7 length returns the # of elements/items/spots in the array!!!

© A+ Computer Science - www.apluscompsci.com for(int r=0; r<mat.length; r++) { } for(int c=0; c<mat[1].length; c++) { out.print(mat[1][c]); } out.println(); OUTPUT 5 3 4 6 int[][] mat = {{5,7},{5,3,4,6},{0,8,9}}; for(int c=0; c<mat[r].length; c++) { out.print(mat[r][c]); } out.println(); OUTPUT 5 7 5 3 4 6 0 8 9

© A+ Computer Science - www.apluscompsci.com int[][] mat = {{5,7},{5,3,4,6},{0,8,9}}; for( int[] row : mat ) { for( int num : row ) { System.out.print( num + " "); } System.out.println(); } OUTPUT 5 7 5 3 4 6 0 8 9

public int countWhitePixels() { int count = 0; for( int[] row : pixelValues ) { for( int item : row ) { if( item == 255 ) count++; } return count; }

public void processImage() { for( int r = 0; r < pixelValues.length-2; r++) { for( int c = 0; c < pixelValues[0].length-2; c++ ) { pixelValues[r][c] -= pixelValues[r+2][c+2]; if( pixelValues[r][c] < BLACK ) pixelValues[r][c] = BLACK; }

© A+ Computer Science - www.apluscompsci.com ArrayList of References / Objects – get,set,remove,add,size – levels of abstraction Matrix / 2 D Array – nested loops, GridWorld ( grid ) GridWorld or Make a Class – location, actor, bug, critter, grid, super, abstract String / Array Question – find biggest, find smallest, etc.

© A+ Computer Science - www.apluscompsci.com -Read all 4 questions before writing anything -answer the easiest question 1 st -most times question 1 is the easiest -see if part B calls part A and so on -many times part C consists of A and B calls -write something on every question -write legibly / use PENCIL!!!!!!!!!! -keep track of your time

© A+ Computer Science - www.apluscompsci.com -When writing methods -use parameter types and names as provided -do not redefine the parameters listed -do not redefine the methods provided -return from all return methods -return correct data type from return methods

© A+ Computer Science - www.apluscompsci.com -When writing a class or methods for a class -know which methods you have -know which instance variables you have -check for public/private on methods/variables -return from all return methods -return correct data type from return methods

© A+ Computer Science - www.apluscompsci.com -When extending a class -know which methods the parent contains -have the original class where you can see it -make sure you have super calls -check for public/private on methods/variables -make super calls in sub class methods as needed

© A+ Computer Science - www.apluscompsci.com -When extending abstract / implementing interface -know which methods the parent contains -have the original class where you can see it -make sure you have super calls -check for public/private on methods/variables -make super calls in sub class methods as needed -implement all abstract methods in sub class

© A+ Computer Science - www.apluscompsci.com -When writing GridWorld question -use the GridWorld quick reference -use original method code when overidding -use Bug and BoxBug code if extending Bug -use Critter and ChameleonCritter code if extending Critter -use Critter and Bug for extends demo -use Critter for ArrayList and Math.random() demo -use GW quick reference on the entire AP test

© A+ Computer Science - www.apluscompsci.com. Visit us at www.apluscompsci.com Full Curriculum Solutions www.apluscompsci.com M/C Review Question Banks.

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