selection csc 171 fall 2004 lecture 8. sequences start end
Post on 21-Dec-2015
218 views
TRANSCRIPT
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”);