Oct8 - 131 slid

Oct 8th

Lab08.

Quiz review

Triangle and Stripes

http://www.slideshare.net/takyeon

Quiz review

No

i++

++i

Use and then increase

int i = 3;

int a = i++; // a = 3, i = 4

int b = ++a; // b = 4, a = 4

Increase and then use

Quiz review

maxCount 100

str

"Hello"

"HELLO"

• Whenever a new variable is declared, it is added to STACK.

• Primitive data types are stored in STACK• byte, short, int, long, float, double, boolean, char

• Other data types are stored in HEAP. • String, Integer, Scanner, …

• Data in HEAP are not immediately deleted but unlinked, and will be garbage-collected.

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

int size = sc.nextInt();

for(int row=1;row<=size;row++) {

for(int col=1;col<=size;col++) {

System.out.print(row*col + " ");

}

System.out.println();

}

}

Lab – 2D drawing

Two methods.

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

M1. Iterate pixels to paint

for (int i=0; i<size; i++) {grid.setColor(i, i, Color.BLUE);

}

Intuitive and efficient

M2. Iterate every pixel, use if conditionals to check pixels to paint

for (int row=0; row<size; row++) {for (int col=0; col<size; col++) {

if(row==col) {grid.setColor(row, col, Color.BLUE);

}}

}

Complex and inefficient BUT! More generalizable

Lab – 2D drawing

Two methods.

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4M2. Iterate every pixel, use if conditionals to check pixels to paint

for (int row=0; row<size; row++) {for (int col=0; col<size; col++) {

if(row!=col) {grid.setColor(row, col, Color.BLUE);

}}

}

You can simply inverse the conditional logic

M1. Iterate pixels to paint

Very difficult

Now you want to paint all the pixels except the diagonal line.

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

More examples.

row>2

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

row%2 == 1

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

col%2 == 1

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

(row-col)>=0

0 -1 -2 -3 -4

1 0 -1 -2 -3

2 1 0 -1 -2

3 2 1 0 -1

4 3 2 1 0

row-col

Diagonal shapes require both row

and col

Linear shapes require either row or col.

Transformation > Move

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

(row+1, col)

(row+1)-col >= 0

-1 -2 -3 -4 -5

0 -1 -2 -3 -4

1 0 -1 -2 -3

2 1 0 -1 -2

3 2 1 0 -1

(row+1)-col

0,1 0,2 0,3 0,4 0,5

1,1 1,2 1,3 1,4 1,5

2,1 2,2 2,3 2,4 2,5

3,1 3,2 3,3 3,4 3,5

4,1 4,2 4,3 4,4 4,5

To move a shape to left by 1 pixel,

replace "row" with "row+1"

Transformation > Horizontal Flip.

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

0,4 0,3 0,2 0,1 0,0

1,4 1,3 1,2 1,1 1,0

2,4 2,3 2,2 2,1 2,0

3,4 3,3 3,2 3,1 3,0

4,4 4,3 4,2 4,1 4,0

HorizontalFlip

(row, 4-col)

(row-(4-col))>=0

-4 -3 -2 -1 0

-3 -2 -1 0 1

-2 -1 0 1 2

-1 0 1 2 3

0 1 2 3 4

row-(4-col)

To flip a shape, multiple row or column by -1, and add size

-col

size-col

col

col

4 := size of the shape – 1Why -1? Because our row and

col index started from 0.

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

VerticalFlip

(4-row, col)

(4-row)-col >= 0

4 3 2 1 0

3 2 1 0 -1

2 1 0 -1 -2

1 0 -1 -2 -3

0 -1 -2 -3 -4

(4-row)-col

4,0 4,1 4,2 4,3 4,4

3,0 3,1 3,2 3,3 3,4

2,0 2,1 2,2 2,3 2,4

1,0 1,1 1,2 1,3 1,4

0,0 0,1 0,2 0,3 0,4

Transformation > Vertical Flip.

(row-col)>=0

0 -1 -2 -3 -4

1 0 -1 -2 -3

2 1 0 -1 -2

3 2 1 0 -1

4 3 2 1 0

(row-(4-col))>=0

-4 -3 -2 -1 0

-3 -2 -1 0 1

-2 -1 0 1 2

-1 0 1 2 3

0 1 2 3 4

HorizontalFlip

(4-row)-col >= 0

4 3 2 1 0

3 2 1 0 -1

2 1 0 -1 -2

1 0 -1 -2 -3

0 -1 -2 -3 -4

Vertical flip

(4-row)-(4-col) >= 0

0 1 2 3 4

-1 0 1 2 3

-2 -1 0 1 2

-3 -2 -1 0 1

-4 -3 -2 -1 0

HorizontalFlip

col-row >= 0

Vertical flip

Oct 6th

Lab07.

Loop applications

public void commonFactor(int n1, int n2) {

for(int i=1; i<=min(n1,n2); i++) {

if(n1%i==0 && n2%i==0) {

System.out.println(i);

}

}

}

Finding common factors of two numbers

Common factors can divide both numbers.E.g. Common factors of 9 and 12 1 and 3

Common factors of 24 and 78 1, 2, 3, and 6

compareTo method

String s1 = "aaa";

String s2 = "aac";

int k = s1.compareTo(s2); // k => -2

Compares s1 and s2 lexicographically. Negative if s1 precedes s2

Positive if s1 follows s2

Zero if s1 is equal to s2

Get multiple words, find the first and the last words

1) Using while loop, keep asking words until "STOP"2) Using compareTo, update the first and the last words3) Print out

Oct 1st

Lab06.

2D drawing

SquareGrid.java

ExampleDriver.java• Prompt a shape question• Create an empty grid• Draw the requested shape

OperatorMaker.java

drawOp (SquareGrid grid, int symbol)

minus, plus, divide, multiply (SquareGrid grid) You will change only these methods

Drawing shapes on 2D grid

Single loop for drawing a line

1) How can we get the middle row number?0

size : 7

3

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

int size = grid.getHt();int midRow = size / 2;

2) How to draw a line?• Iterate over columns (0 – 4)

• Paint the middle cell

for (int iCol=0; iCol<size; iCol++) {grid.setColor(midRow, iCol, Color.BLUE);

}

Single loop for drawing a line

1) How can we get the middle column number?0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

int size = grid.getWd();int midCol = size / 2;

2) How to draw a line?• Iterate over rows (0 – 4)

• Paint the middle cell

for (int iRow=0; iRow<size; iRow++) {grid.setColor(iRow, midCol, Color.BLUE);

}

Notice that drawing horizontal and vertical lines are quite similar. We just switched row and column variables.

Single loop for drawing a line

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

1) How to draw a line?• Iterate over rows or columns (0-4)

• Paint diagonal cells.

for (int iRow=0; iRow<size; iRow++) {grid.setColor(iRow, iRow, Color.BLUE);

}

for (int iCol=0; iCol<size; iCol++) {grid.setColor(midRow, iCol, Color.BLUE);

}

for (int iRow=0; iRow<size; iRow++) {grid.setColor(iRow, midCol, Color.BLUE);

}

for (int iRow=0; iRow<size; iRow++) {grid.setColor(iRow, iRow, Color.BLUE);

}

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3 2,4

3,0 3,1 3,2 3,3 3,4

4,0 4,1 4,2 4,3 4,4

for (int iCol=0; iCol<size; iCol++) {grid.setColor(iCol, iCol, Color.BLUE);

}

or

Single loop for drawing a line

Iterating over the columns, paint the middle cell.

Iterating over the columns, paint the middle cell.

Iterating over the rows, paint the center cell.

Iterating over the columns, paint i-th cell.

Draw Plus, Divide, and Divide (rotated).

Sep 29th

Lab05.1. Recap the quiz #1

2. String Class

3. static vs. instance method

Recap quiz #1.

PRINT your names in the grade server. NO nicknames.

Recap quiz #1.

Use specific technical keywordse.g. What does CVS “do” for us?

1. Check out / Download the starter files2. Store / Save multiple versions of the source codeshare, deliver, get, access, connected people, ...

Penalties for inaccurate extra infoe.g. CVS runs our code and give us grades. -1 for incorrect extra info.

String Class

String s = “hello”;

Create a new String object with an initial value “hello”

String objects have many convenient methods,

upperS = s.toUpperCase(); // will set upperS to “HELLO”

whereIsl= s.indexOf(‘l’); // will find the position of the first ‘l’

newS = s.replace(‘e’,’a’); // will set newS to “hallo”

int type vs. Integer Class

int i=0;

Primitive data type

Integer i = 17;

Wrapper Class

don’t have much method provide methods

- convert to string

- generate hash codes

Faster A little slower

Static vs. Instance method

Intance methods need a sheep as a subject.

bob.eat();

bob.smileTo(clara);

bob.getPenNumber();

Static methods are about all the sheeps.

Sheep.getTotalSheep();

Sheep.removeAll();

Sheep.addSheep(‘evan’);

Sep 24th

Lab04.Loop

Flow of Control

1. Top-to-bottom statements

2. Method calls

3. Conditional statements

4. Iteration (loop)for, while, ...

Two goals of iteration

1. AutomationReduce repetition of code

System.out.println(“****”);

System.out.println(“****”);

System.out.println(“****”);

How can we reduce?for(int i=0;i<3;i++) {

System.out.println(“****”);

}

2. AbstractionCode for various situations

System.out.println(“****”);

How can we print n-number of “*”?

From manual & concrete to automatic & abstract

Level 1. Draw 30 by 10 rectangle (hard-coded) System.out.println(“**********”);

System.out.println(“**********”);

System.out.println(“**********”);

... 27 more lines

Level 2. Draw 30 by 10 rectangle (single-loop)

Too many copy & paste. Hard to modify.

int row=0;

while(row<30) {

System.out.println(“**********”);

row++;

}

A little more compact. Still too many * for each line.

From manual & concrete to automatic & abstract

Level 3. Draw 30 by 10 rectangle (nested-loop) int row=0, col=0;

while(row<30) {

while(col<10) {

System.out.print(“*”);

}

System.out.println();

}

Much compact. Cannot change # of row and col

Level 4. Draw height by width (nested-loop, parameterized) int row=0, col=0;

int height=30, width=10;

while(row<height) {

while(col<width) {

System.out.print(“*”);

}

System.out.println();

} Compact Can draw any sized rectangle

iterartorline 1

0

valueline 2

0

targetline 4

answerline 1

1

iline 1

1

jline 1

0