Download - Control Structures Lecture 3
Control StructuresLecture 3
Instructors: Fu-Chiung Cheng
(鄭福炯 )Associate Professor
Computer Science & EngineeringTatung University
email: [email protected]:// www.cse.ttu.edu.tw/~cheng
Contents: Control Structures
• DecisionUsing if and if...elseNested if StatementsShortcut if StatementsUsing switch Statements
• RepetitionLooping: for, while, and doNested loopsUsing break and continue
Decisions
if Statements
switch Statements
Shortcut if Statements
if Statements
Format:Format:if (booleanExpression) if (booleanExpression) { {
statement(s);statement(s);}}
Example:Example:if ((i >= 0) && (i <= 10)) if ((i >= 0) && (i <= 10)) System.out.println("i is between 0 and 10");System.out.println("i is between 0 and 10");
The if...else Statement Format:Format:if (booleanExpression) if (booleanExpression) { { statement(s)-for-the-true-case;statement(s)-for-the-true-case;}}else else {{ statement(s)-for-the-false-case;statement(s)-for-the-false-case;}}
if...else Example
if (radius >= 0)if (radius >= 0){ { area = radius*radius*PI;area = radius*radius*PI; System.out.println("The area for the System.out.println("The area for the circle of radius " + radius + " is " + area);circle of radius " + radius + " is " + area);}}elseelse{{ System.out.println("Negative input");System.out.println("Negative input");}}
Nested if Statements
Example 3.1: Using Nested if Example 3.1: Using Nested if StatementsStatements
This program reads in year and loan This program reads in year and loan amount and computes the monthly amount and computes the monthly pay and total pay. The interest rate is pay and total pay. The interest rate is determined by year. determined by year.
TestIfElseTestIfElse Run
Shortcut if Statements
if (x > 0) y = 1if (x > 0) y = 1else y = -1;else y = -1;
is equivalent tois equivalent to
y = (x > 0) ? 1 : -1;y = (x > 0) ? 1 : -1;
switch Statements
switch (year)switch (year){ { case 7: interestRate = 7.25;case 7: interestRate = 7.25; break;break; case 15: interestRate = 8.50;case 15: interestRate = 8.50; break;break; case 30: interestRate = 9.0;case 30: interestRate = 9.0; break;break; default: System.out.println(default: System.out.println( "Wrong Year, enter 7, 15, or 30");"Wrong Year, enter 7, 15, or 30");}}
switch Statement Flow Chart
Repetitions
for Loops
while Loops
do Loops
break and continue
for Loops Format:Format:
for (control-variable-initializer;for (control-variable-initializer; continue-condition; adjustment-statement)continue-condition; adjustment-statement)
{{ //loop body;//loop body;
}}
Example:Example:int i;int i;for (i = 0; i<100; i++)for (i = 0; i<100; i++){{
System.out.println("Welcome to Java!” + i); System.out.println("Welcome to Java!” + i); }}
// for (int i = 0; i<100; i++) // for (int i = 0; i<100; i++)
for Loop Flow Chart
for Loop Examples
Examples for using the for loop:
Example 3.2: TestSum.java
TestSumTestSum
TestMulTableTestMulTable
Example 3.3: TestMulTable.java
Run
Run
while Loops Format:Format:
while (continue-condition) while (continue-condition) {{ // loop-body;// loop-body;}}
ExampleExample 3.4: TestWhile.java3.4: TestWhile.java
TestWhileTestWhile Run
while Loop Flow Chart
do Loops Format:Format:
dodo{{ //loop body;//loop body;} while (continue-condition)} while (continue-condition)
do Loop Flow Chart
The break Keyword
The continue Keyword
Using break and continue
Examples for using the break and continue keywords:
Example 3.5: TestBreak.java
Example 3.6: TestContinue.java
TestBreakTestBreak
TestContinueTestContinue
Run
Run