Java程序辅导

Lab 7 
CSE 15L 
Winter 2009 
Scott B. Baden 
UCSD 
3/1/09 Scott B. Baden /CSE 15L / Winter '09 2 
Announcements 
•  No Lab next time 
•  We will  have our usual weekly quiz 
•  Final Exam Review 
3/1/09 Scott B. Baden /CSE 15L / Winter '09 3 
Filled, named polygons 
•  This time we will draw polygons using more powerful constructs 
–  java Lab7  shapes.in 
•  Copies of named polygons may be drawn at arbitrary places 
–  Define polygons with P 
–  Add the polygon to the canvas with A 
•  M, R, L, U, D as before 
    P tri 50 50 0 0 50 0 50 25
    P sq 50 50 10 10 10 40 40 40 40 10
    M 10 10
    A tri
    R 50
    C red
    A sq 
3/1/09 Scott B. Baden /CSE 15L / Spring '08 4 
Jz.in 
M 14 5 
A jd 
C red 
M 14 0 
A jd 
C green 
M 14 0 
A jd 
C blue 
M 14 0 
A jd 
M -42 21 
A jd 
C red 
M 14 21 
A jd 
C green 
M 14 21 
A jd 
C blue 
M 14 21 
P jd 14 20 6 10 0 10 0 12 6 12 6 14 4 16 4 18 6 20 8 
20 10 18 10 16 8 14 8 12 10 12 10 14 12 14 12 10 8 10 
8 8 10 0 8 0 7 4 6 0 4 0 6 8 
3/1/09 Scott B. Baden /CSE 15L / Winter '09 5 
Other files 
•  Inputs together with screenshots  of the image  in the  Lab7 directory 
–  tri.in 
–  JDs.in 
•  Error input: odd number of points in a polygon: oddError.in 
   Odd number of coordinate points 
3/1/09 Scott B. Baden /CSE 15L / Winter '09 6 
Miscellany 
•  You will need the GraphicsUtil Library 
–  Co-located with the lab source 
–  Compile GraphicsUtil.java 
–  http://www.apl.jhu.edu/~hall/java/GraphicsUtil.html 
•  Global origin (0,0) is at the upper left corner 
–  Pen’s initial position is at the center 
–  Program scales coordinates so output is easier to view 
–  Reports out of bound coordinates 
•  As before 
–  Each polygon has a defined bounding box 
–  Coordinates within the bounding box are relative to the lower left 
corner 
P tri 50 50 0 0 50 0 50 25 
M 10 10 
A tri 
(0,0) (10,10) 
    50 
    50 
3/1/09 Scott B. Baden /CSE 15L / Winter '09 7 
Sidebar on Hash Tables 
•  A hash table is a data structure that maps keys onto records 
•  In our case the keys are polygon names, the records are the 
polygon descriptions 
•  An array is a special case  
http://en.wikipedia.org/wiki/Hash_table 
3/1/09 Scott B. Baden /CSE 15L / Winter '09 8 
Başla !