selection csc 171 fall 2004 lecture 8. sequences start end

SELECTIONSELECTION

CSC 171 FALL 2004

LECTURE 8

SequencesSequencesstart

end

Example methodExample methodpublic static void main(String[] args) {

int a;a = 1 ;System.out.println(“a == “ + a); a = a + a + a;System.out.println(“a == “ + a); a = a * a * a;System.out.println(“a == “ + a);

}

Same statements?Same statements?public static void main(String[] args) {

int a;a = 1 ;System.out.println(“a == “ + a); a = a + a + a;System.out.println(“a == “ + a); a = a * a * a;System.out.println(“a == “ + a);

}

Sequence StatementsSequence Statementspublic static void main(String[] args) {

int a;a = 1 ;System.out.println(“a == “ + a);//1a = a + a + a;System.out.println(“a == “ + a); //3a = a * a * a;System.out.println(“a == “ + a);// 27

}

start main()

a=1;

end main()

a=a+a+a;

a=a*a*a;

System.out.println(“a == “ + a);

System.out.println(“a == “ + a);

System.out.println(“a == “ + a);

start main()

a=1;

System.out.println(“a == “ + a);

a=a+a+a;

System.out.println(“a == “ + a);

a=a*a*a;

System.out.println(“a == “ + a);

end main()

1 a

3 27

SequencesSequencesstart

end

Sequence branchingSequence branchingstart

end

Sequence branchingSequence branchingstart

end

Sequence branchingSequence branchingstart

end

Sequence branchingSequence branchingstart

a=1;

end

a=a+a; a=a*a

System.out.println(“a == “ + a);

a<3true false

Sequence branchingSequence branchingstart

a=1;

end

a=a+a;

System.out.println(“a == “ + a);

a<3true

Sequence branchingSequence branchingstart

a=6;

end

a=a*a

System.out.println(“a == “ + a);

a<3false

Sequence BranchingSequence Branchingpublic static void main(String[] args) {

int a;a = 1 ;if (a < 3) {

a = a + a;} else {

a = a * a;}System.out.println(“a == “ + a);//2

}

Sequence BranchingSequence Branchingpublic static void main(String[] args) {

int a;a = 6 ;if (a < 3) {

a = a + a;} else {

a = a * a;}System.out.println(“a == “ + a);//36

}

Slightly more practicalSlightly more practicalstart

READ INCOME

end

tax = income * .3; tax = income * .4

System.out.println(“take home == “ + (income-tax) );

income < 75000true false

Review Reading NumbersReview Reading Numbersstatic double myGetDouble() {

String localInput = "";InputStreamReader reader =

new InputStreamReader(System.in);BufferedReader console = new BufferedReader(reader)try { localInput = console.readLine(); }catch (IOException e) { System.out.println(e + " bad read "); System.exit(0);}return Double.parseDouble(localInput);

}

Sequence BranchingSequence Branchingpublic static void main(String[] args) {

double income, tax;final double taxRate1 = 0.3, taxRate2 = 0.4;income = getMyDouble() ;if (income < 75000) {

tax = income * taxRate1;} else {

tax = income * taxRate2;}System.out.println(“take == “ + (income - tax));

}

BlocksBlocksOn single statements brackets are optional

if (x < 4)System.out.println(“x less than 4”);

else System.out.println(“x is not less than

4”);But Beware:

if (x < 4)System.out.println(“x less than 4”);

System.out.println(“that’s a small num!”);

Else is optionalElse is optionalif (income > 120000)

tax = tax + (income * extraTaxRate);

““simple” if branchingsimple” if branchingstart

end

true

false

?

What about the conditions?What about the conditions?if (income > 120000)

tax = tax + (income * extraTaxRate);

These are “boolean” expressionsThey have a value of “true” or “false”

Relational OperatorsRelational Operators< // less than<= // less than or equal to> // greater than>= // greater than or equal

to == // equal to!= // not equal to

Can be used in clausesCan be used in clauses

double income = 73000.0;

if (income > 120000.0) System.out.println(“Pay up!”);

Can be abstractedCan be abstractedboolean b1;double income = 73000.0;b1 = ( income > 120000.0);if (b1)

System.out.println(“Pay up!”);

Using “AND”Using “AND”

double inc = 73000.0;int numChild = 5;if ((inc < 50000.0) && (numChild >

3))System.out.println(“Pay less”);

Using “OR”Using “OR”

double inc = 73000.0;int numChild = 5;if ((inc < 50000.0) || (numChild > 3))

System.out.println(“Pay less”);

Using “NOT”Using “NOT”

double inc = 73000.0;int numChild = 5;if !(!(inc < 50000.0) && !(numChild >

3))System.out.println(“Pay less”);