This shows you the differences between two versions of the page.
Both sides previous revision Previous revision Next revision | Previous revision Next revision Both sides next revision | ||
java:control_flow [2015/02/09 04:57] gthanos [for statement] |
java:control_flow [2016/02/26 11:15] 127.0.0.1 external edit |
||
---|---|---|---|
Line 1: | Line 1: | ||
- | ====== Έλεγχος ροής προγράμματος ====== | + | ====== Ροή προγράμματος ====== |
- | Αναφορικά με τον έλεγχο ροής προγράμματος μπορείτε (//for,while,do-while,if,switch// κλπ) να ανατρέξετε στο documentation της Oracle [[ http://docs.oracle.com/javase/tutorial/java/nutsandbolts/flow.html | εδώ]]. | + | Συμπληρωματικά, για τον έλεγχο ροής προγράμματος (//for,while,do-while,if,switch// κλπ.) μπορείτε να ανατρέξετε στο documentation της Oracle [[ http://docs.oracle.com/javase/tutorial/java/nutsandbolts/flow.html | εδώ]]. |
- | ===== if - else if - else statement ===== | + | * [[java:control_flow_statements | Εντολές ελέγχου ροής προγράμματος ]] |
+ | * [[java:loop_statements | Εντολές ανακύκλωσης ]] | ||
+ | * [[java:break_loop_statements | Εντολές τερματισμού και ελέγχου ανακύκλωσης ]] | ||
- | Ανάλογά με την γλώσσα C. Δείτε το παρακάτω παράδειγμα. | ||
- | <code java IfElseDemo.java> | ||
- | class IfElseDemo { | ||
- | public static void main(String[] args) { | ||
- | int testscore = 76; | + | | Προηγούμενο: [[:java:operators | Τελεστές ]] | [[:toc | Περιεχόμενα ]] | Επόμενο: [[:java:control_flow_statements | Εντολές ελέγχου ροής προγράμματος ]] | |
- | char grade; | + | |
- | + | ||
- | if (testscore >= 90) { | + | |
- | grade = 'A'; | + | |
- | } else if (testscore >= 80) { | + | |
- | grade = 'B'; | + | |
- | } else if (testscore >= 70) { | + | |
- | grade = 'C'; | + | |
- | } else if (testscore >= 60) { | + | |
- | grade = 'D'; | + | |
- | } else { | + | |
- | grade = 'F'; | + | |
- | } | + | |
- | System.out.println("Grade = " + grade); | + | |
- | } | + | |
- | } | + | |
- | </code> | + | |
- | + | ||
- | ===== Switch statement ===== | + | |
- | + | ||
- | Σε αναλογία με την γλώσσα C, η Java υποστηρίζει την εντολή switch. Η ιδιαιτερότητα της switch στην Java είναι ότι υποστηρίζει ακεραίους, enumerated types ή αλφαριθμητικά. Δείτε τα παρακάτω παραδείγματα με χρήση ακεραίων και αλφαριμθητικών. | + | |
- | + | ||
- | <code java SwitchDemo.java> | + | |
- | public class SwitchDemo { | + | |
- | public static void main(String[] args) { | + | |
- | + | ||
- | int month = 8; | + | |
- | String monthString; | + | |
- | switch (month) { | + | |
- | case 1: monthString = "January"; | + | |
- | break; | + | |
- | case 2: monthString = "February"; | + | |
- | break; | + | |
- | case 3: monthString = "March"; | + | |
- | break; | + | |
- | case 4: monthString = "April"; | + | |
- | break; | + | |
- | case 5: monthString = "May"; | + | |
- | break; | + | |
- | case 6: monthString = "June"; | + | |
- | break; | + | |
- | case 7: monthString = "July"; | + | |
- | break; | + | |
- | case 8: monthString = "August"; | + | |
- | break; | + | |
- | case 9: monthString = "September"; | + | |
- | break; | + | |
- | case 10: monthString = "October"; | + | |
- | break; | + | |
- | case 11: monthString = "November"; | + | |
- | break; | + | |
- | case 12: monthString = "December"; | + | |
- | break; | + | |
- | default: monthString = "Invalid month"; | + | |
- | break; | + | |
- | } | + | |
- | System.out.println(monthString); | + | |
- | } | + | |
- | } | + | |
- | </code> | + | |
- | + | ||
- | <code java StringSwitchDemo.java> | + | |
- | public class StringSwitchDemo { | + | |
- | + | ||
- | public static int getMonthNumber(String month) { | + | |
- | + | ||
- | int monthNumber = 0; | + | |
- | + | ||
- | if (month == null) { | + | |
- | return monthNumber; | + | |
- | } | + | |
- | + | ||
- | switch (month.toLowerCase()) { | + | |
- | case "january": | + | |
- | monthNumber = 1; | + | |
- | break; | + | |
- | case "february": | + | |
- | monthNumber = 2; | + | |
- | break; | + | |
- | case "march": | + | |
- | monthNumber = 3; | + | |
- | break; | + | |
- | case "april": | + | |
- | monthNumber = 4; | + | |
- | break; | + | |
- | case "may": | + | |
- | monthNumber = 5; | + | |
- | break; | + | |
- | case "june": | + | |
- | monthNumber = 6; | + | |
- | break; | + | |
- | case "july": | + | |
- | monthNumber = 7; | + | |
- | break; | + | |
- | case "august": | + | |
- | monthNumber = 8; | + | |
- | break; | + | |
- | case "september": | + | |
- | monthNumber = 9; | + | |
- | break; | + | |
- | case "october": | + | |
- | monthNumber = 10; | + | |
- | break; | + | |
- | case "november": | + | |
- | monthNumber = 11; | + | |
- | break; | + | |
- | case "december": | + | |
- | monthNumber = 12; | + | |
- | break; | + | |
- | default: | + | |
- | monthNumber = 0; | + | |
- | break; | + | |
- | } | + | |
- | + | ||
- | return monthNumber; | + | |
- | } | + | |
- | + | ||
- | public static void main(String[] args) { | + | |
- | + | ||
- | String month = "August"; | + | |
- | + | ||
- | int returnedMonthNumber = | + | |
- | StringSwitchDemo.getMonthNumber(month); | + | |
- | + | ||
- | if (returnedMonthNumber == 0) { | + | |
- | System.out.println("Invalid month"); | + | |
- | } else { | + | |
- | System.out.println(returnedMonthNumber); | + | |
- | } | + | |
- | } | + | |
- | } | + | |
- | </code> | + | |
- | + | ||
- | ===== While και do-while statements ===== | + | |
- | + | ||
- | + | ||
- | <code java WhileDemo.java> | + | |
- | class WhileDemo { | + | |
- | public static void main(String[] args){ | + | |
- | int count = 1; | + | |
- | while (count < 11) { | + | |
- | System.out.println("Count is: " + count); | + | |
- | count++; | + | |
- | } | + | |
- | } | + | |
- | } | + | |
- | </code> | + | |
- | + | ||
- | <code java DoWhileDemo.java> | + | |
- | class DoWhileDemo { | + | |
- | public static void main(String[] args){ | + | |
- | int count = 1; | + | |
- | do { | + | |
- | System.out.println("Count is: " + count); | + | |
- | count++; | + | |
- | } while (count < 11); | + | |
- | } | + | |
- | } | + | |
- | </code> | + | |
- | + | ||
- | + | ||
- | ===== for statement ===== | + | |
- | + | ||
- | Η εντολή ''for'' συντάσσεται όπως και στην γλώσσα προγραμματισμού C. Ενδιαφέρον έχει μία διαφοροποιημένη έκδοση της ''for'' που υποστηρίζει η java και παρουσιάζουμε εδώ με σκοπό την ανακύκλωση σε όλα τα μέλη ενός πίνακα ή ενός [[http://docs.oracle.com/javase/tutorial/collections/index.html |Collection]] (όπως θα δούμε αργότερα). Δείτε το παρακάτω παράδειγμα. | + | |
- | + | ||
- | <code java EnhancedForDemo.java> | + | |
- | class EnhancedForDemo { | + | |
- | public static void main(String[] args){ | + | |
- | int[] numbers = | + | |
- | {1,2,3,4,5,6,7,8,9,10}; | + | |
- | for (int item : numbers) { | + | |
- | System.out.println("Count is: " + item); | + | |
- | } | + | |
- | } | + | |
- | } | + | |
- | </code> | + | |
- | + | ||
- | + | ||
- | + | ||
- | |[[:java:operators | Τελεστές ]] | [[:java: | ]] | | + | |