Post on 03-Jul-2018
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Thisdocumentiscopyright(C)StanfordComputerScienceandMartyStepp,licensedunderCreativeCommonsAttribution2.5License.Allrightsreserved.BasedonslidescreatedbyKeithSchwarz,MehranSahami,EricRoberts,StuartReges,andothers.
CS106A,Lecture27FinalExamReview1
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Plan for today•Announcements/Examlogistics•Graphics,Animation,Events•1DArrays•2DArrays•ArrayList
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Plan for today•Announcements/Examlogistics•Graphics,Animation,Events•1DArrays•2DArrays•ArrayList
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Final exam• Isthe finalexam cumulative?• What will betested on the finalexam?• What about allthis stuff you aren’t covering today?
– ExpressionsandVariables– JavaControlStatements– ConsolePrograms– Methods,parameters,returns– Randomness– Strings andchars– Scanners andfileprocessing– Memory
• Isthe finalexam going tobedifficult/curved?• Howcan Ipractice forthe final?
Midterm review sessionwas the recorded sectionon Fridayof Week 4
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Practicing for the final• Reviewconceptsyou’reunsureof• Reviewconceptsfrompreviousassignments• Dosectionproblems• Dopracticefinalunderrealconditions• codestepbystep.com
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Plan for today•Announcements/Examlogistics•Graphics,Animation,Events•1DArrays•2DArrays•ArrayList
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Graphics• LookatlectureslidesforlistsofdifferentGObject typesandtheirmethods
• Remember:thexandyofGRect,GOval,etc.Istheirupperleftcorner,butthexandyofGLabel isitsleftmostbaselinecoordinate.
• Rememberforlabels:getHeight()=getAscent()+getDescent().
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AnimationStandardformatforanimationcode:
while (condition) {update graphicsperform checkspause(PAUSE_TIME);
}
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Events• TwowaysforJavatorunyourcode:fromrun()andfromeventhandlers(mouseClicked,mouseMoved,actionPerformed,etc.)
• Eventhandlersmusthaveexactlythespecifiedsignatureotherwisetheywon’twork!
e.g.public void mouseClicked(MouseEvent e)
• Ifyouneedtomodifysomethinginaneventhandlerthatyouuseelsewhereinyourcode,itshouldbeaninstancevariable(e.g.paddleinBreakout!)
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Demo: Seeker
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Seeker• Redsquareisthetarget• Transparentsquareistheseeker• Theseekershouldmovetowardsandengulfthetarget• Canchangetargetlocationbyclickingonthescreen
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Instance variables
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run()public void run() {
initTarget();initSeeker();
// Always keep seeking the targetwhile (true) {
seek();pause(PAUSE_TIME);
}}
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run()public void run() {
initTarget();initSeeker();
// Always keep seeking the targetwhile (true) {
seek();pause(PAUSE_TIME);
}}
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initTarget()
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initSeeker()
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run()public void run() {
initTarget();initSeeker();
// Always keep seeking the targetwhile (true) {
seek();pause(PAUSE_TIME);
}}
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seek()
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moveAmount()
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mouseClicked()
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Plan for today•Announcements/Examlogistics•Graphics,Animation,Events•1DArrays•2DArrays•ArrayList
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1D Arrays• Anarray isafixed-lengthlistofasingletypeofthing.• Anarraycanstoreprimitives andobjects.• Youcannotcallmethodsonarraysi.e.nomyArray.contains().• GetthelengthbysayingmyArray.length.(Noparentheses!)• PrintarraywithArrays.toString(myArray),not println(myArray)!
[2, 4, 6, 8] [I@4ddced80
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Program traces• Localvariablesareseparate acrossmethods• Parametersarejustassignednamesbytheorderinwhichthey’repassed
• Drawchangestovariablesasyougothroughtheprogram• Objectsvsprimitivebehaviorforparameters
A.Prints [5,10,15]5B.Prints [5,10,15]7C.Prints [5,20,15]5D.Prints [5,20,15]7
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Trace
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Trace
Output:[4, 0, 2] 4 1[4, 0, 2] 3[8, 0, 4] 1 1[8, 0, 4] 6
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Extra 1D Array problemWritethe method int longestSortedSequence(int[] array)
e.g.int[] array = {3, 8, 10, 1, 9, 14, -3, 0, 14, 207, 56, 98, 12}
Sorted inthis casemeans nondecreasing,soasequence could contain duplicates:
e.g.int[] array = {17, 42, 3, 5, 5, 5, 8, 2, 4, 6, 1, 19}
Link:http://www.codestepbystep.com/problem/view/java/arrays/longestSortedSequence
3 3 4 2 1
2 3 25
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Plan for today•Announcements/Examlogistics•Graphics,Animation,Events•1DArrays•2DArrays•ArrayList
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2D Arrays = Arrays of Arrays!int[][] a = new int[3][4];
a[0][0] a[0][1] a[0][2] a[0][3]
a[1][0] a[1][1] a[1][2] a[1][3]
a[2][0] a[2][1] a[2][2] a[2][3]
Outerarray
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Chess• Knight:moves inan”L”-shape (two steps inone direction,one stepinaperpendicular direction)
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knightCanMove()boolean knightCanMove(String[][] board,
int startRow, int startCol,int endRow, int endCol)
• (startRow,startCol)mustcontainaknight• (endRow,endCol)mustbeempty• (endRow,endCol)mustbereachablefrom(startRow,startCol)inasinglemove
• Assumethat(startRow,startCol)and(endRow,endCol)arewithinboundsofarray
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knightCanMove()
0 1 2 3 4 5 6 7
0 ”king”
1 ”knight”
2
3 ”rook”
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7
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0 1 2 3 4 5 6 7
0 ”king”
1 ”knight”
2
3 ”rook”
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knightCanMove()
0 1 2 3 4 5 6 7
0 ”king”
1 ”knight”
2
3 ”rook”
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knightCanMove(board, 2, 2, 3, 4)
Noknight at(2,2)
returns false
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0 1 2 3 4 5 6 7
0 ”king”
1 ”knight”
2
3 ”rook”
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knightCanMove()
0 1 2 3 4 5 6 7
0 ”king”
1 ”knight”
2
3 ”rook”
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knightCanMove(board, 1, 2, 0, 4)
Spaceoccupied
returns false
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knightCanMove()
0 1 2 3 4 5 6 7
0 ”king”
1 ”knight”
2
3 ”rook”
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knightCanMove(board, 1, 2, 3, 2)
(1,2)to(3,2)isnotavalidmove
returns false
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knightCanMove()
0 1 2 3 4 5 6 7
0 ”king”
1 ”knight”
2
3 ”rook”
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knightCanMove(board, 1, 2, 3, 3)
Knightisat(1,2)and(3,3)isemptyand(1,2)->(3,3)isavalidmove
returns true
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knightCanMove()// This method returns true if the starting square contains a knight,// the end square is empty, and the knight can legally move from the// start square to the end square.private boolean knightCanMove(String[][] board, int startRow,
int startCol, int endRow, int endCol) {
}
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knightCanMove()// This method returns true if the starting square contains a knight,// the end square is empty, and the knight can legally move from the// start square to the end square.private boolean knightCanMove(String[][] board, int startRow,
int startCol, int endRow, int endCol) {if (board[startRow][startCol].equals("knight")) {
}
}
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knightCanMove()// This method returns true if the starting square contains a knight,// the end square is empty, and the knight can legally move from the// start square to the end square.private boolean knightCanMove(String[][] board, int startRow,
int startCol, int endRow, int endCol) {if (board[startRow][startCol].equals("knight")) {
if (board[endRow][endCol].equals("")) {
}}
}
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knightCanMove()// This method returns true if the starting square contains a knight,// the end square is empty, and the knight can legally move from the// start square to the end square.private boolean knightCanMove(String[][] board, int startRow,
int startCol, int endRow, int endCol) {if (board[startRow][startCol].equals("knight")) {
if (board[endRow][endCol].equals("")) {int rowDifference = Math.abs(startRow - endRow);int colDifference = Math.abs(startCol - endCol);if ((rowDifference == 1 && colDifference == 2) ||
(rowDifference == 2 && colDifference == 1)) {return true;
}}
}
}
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knightCanMove()// This method returns true if the starting square contains a knight,// the end square is empty, and the knight can legally move from the// start square to the end square.private boolean knightCanMove(String[][] board, int startRow,
int startCol, int endRow, int endCol) {if (board[startRow][startCol].equals("knight")) {
if (board[endRow][endCol].equals("")) {int rowDifference = Math.abs(startRow - endRow);int colDifference = Math.abs(startCol - endCol);if ((rowDifference == 1 && colDifference == 2) ||
(rowDifference == 2 && colDifference == 1)) {return true;
}}
}return false;
}
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Plan for today•Announcements/Examlogistics•Graphics,Animation,Events•1DArrays•2DArrays•ArrayList
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ArrayList• AnArrayList isaflexible-lengthlistofasingletypeofthing.• AnArrayList canonlystoreobjects.
– Forprimitivesusee.g.ArrayList<Integer> insteadofArrayList<int>.(Integer isawrapperclassforint)
– Otherwrapperclasses:Double insteadofdouble,Character insteadofchar,Boolean insteadofboolean.
• AnArrayList hasavarietyofmethodsyoucanuselike.contains,.get,.add,.remove,.size,etc.
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Array vs ArrayList• Array
– Fixedsize– Efficient(notaconcerninthisclass)– Nomethods,canonlyusemyArray.length (noparentheses!)– Canstoreanyobjectorprimitive
• ArrayList– Expandable– LessefficientthanArray(notaconcerninthisclass)– Convenientmethodslike.add(),.remove(),.contains()– Cannotstoreprimitives,sousetheirwrapperclassesinstead
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deleteDuplicates()private void deleteDuplicates(ArrayList<String> list)
• Guaranteedthatlistisinsortedorder• {"be","be","is","not","or","question","that","the","to","to"}becomes{“be”,“is”,“not”,“or”,“question”,“that”,“the”,“to”}
• Solutionstrategy:– LoopthroughArrayList– Comparepairsofelements– Ifelement.equals(nextElement),removeelementfromthelist
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deleteDuplicates• LoopthroughArrayList• Comparepairsofelements• Ifelement.equals(nextElement),removeelementfromthelist
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deleteDuplicatesReverse• LoopthroughArrayList inreverse• Comparepairsofelements• Ifelement.equals(previousElement),removeelementfromthelist
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Recap•Announcements/Examlogistics•Graphics,Animation,Events•1DArrays•2DArrays•ArrayList
Nexttime:FinalExamReview2