Control Structures Lecture 3

1. Instructors: Fu-Chiung Cheng (鄭福炯) Associate Professor Computer Science & Engineering Tatung University email: cheng@cse.ttu.edu.tw http:// www.cse.ttu.edu.tw/~cheng Control StructuresLecture 3

2. 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 Contents: Control Structures

3. Decisions if Statements switch Statements Shortcut if Statements

4. if Statements • Format: if (booleanExpression) { statement(s); } • Example: if ((i >= 0) && (i <= 10)) System.out.println("i is between 0 and 10");

5. The if...else Statement • Format: if (booleanExpression) { statement(s)-for-the-true-case; } else { statement(s)-for-the-false-case; }

6. if...else Example if (radius >= 0) { area = radius*radius*PI; System.out.println("The area for the circle of radius " + radius + " is " + area); } else { System.out.println("Negative input"); }

7. 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

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

9. switch Statements switch (year) { case 7: interestRate = 7.25; break; case 15: interestRate = 8.50; break; case 30: interestRate = 9.0; break; default: System.out.println( "Wrong Year, enter 7, 15, or 30"); }

10. switch Statement Flow Chart

11. Repetitions for Loops while Loops do Loops break and continue

12. for Loops • Format: for (control-variable-initializer; continue-condition; adjustment-statement) { //loop body; } • Example: int i; for (i = 0; i<100; i++) { System.out.println("Welcome to Java!” + i); } // for (int i = 0; i<100; i++)

13. for Loop Flow Chart

14. for Loop Examples • Examples for using the for loop: • Example 3.2: TestSum.java TestSum • Example 3.3: TestMulTable.java TestMulTable

15. while Loops • Format: while (continue-condition) { // loop-body; } • Example3.4: TestWhile.java TestWhile

16. while Loop Flow Chart

17. do Loops • Format: do { //loop body; } while (continue-condition)

18. do Loop Flow Chart

19. The break Keyword

20. The continue Keyword

21. Using break and continue Examples for using the break and continue keywords: • Example 3.5: TestBreak.java TestBreak • Example 3.6: TestContinue.java TestContinue