Control Structures Lecture 3 Instructors: Fu-Chiung Cheng ( 鄭福炯 ) Associate Professor Computer Science & Engineering Tatung University

Contents: Control Structures Decision  Using if and if...else  Nested if Statements  Shortcut if Statements  Using switch Statements Repetition  Looping: for, while, and do  Nested loops  Using break and continue

Decisions if Statements switch Statements Shortcut if Statements

if Statements Format: Format: if (booleanExpression) { statement(s); statement(s);} Example: Example: if ((i >= 0) && (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) { statement(s)-for-the-true-case; statement(s)-for-the-true-case;}else{ statement(s)-for-the-false-case; statement(s)-for-the-false-case;}

if...else Example 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);}else{ System.out.println("Negative input"); System.out.println("Negative input");}

Nested if Statements Example 3.1: Using Nested if Statements This program reads in year and loan amount and computes the monthly pay and total pay. The interest rate is determined by year. TestIfElse

Shortcut if Statements if (x > 0) y = 1 else y = -1; is equivalent to y = (x > 0) ? 1 : -1;

switch Statements 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; continue-condition; adjustment-statement) continue-condition; adjustment-statement){ //loop body; //loop body;} Example: Example: int 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: F Example 3.2: TestSum.java TestSum TestMulTable F Example 3.3: TestMulTable.java

while Loops Format: Format: while (continue-condition) { // loop-body; // loop-body;} Example 3.4: TestWhile.java Example 3.4: TestWhile.java TestWhile

while Loop Flow Chart

do Loops Format: Format:do{ //loop body; //loop body; } 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: F Example 3.5: TestBreak.java F Example 3.6: TestContinue.java TestBreak TestContinue