oop - Defining Values of Fields as Constants in Java -

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i'm implementing standard object oriented library in java. standard includes many messages passing on network through terminals. every message implemented single class.

some of fields represented char types , fields have 1 of values defined in standard. example,

public class outgoingmessage {     private char action;

and action has these values,

'0' - not print '1' - print '2' - print , forward '3' - print , reply 'f' - forward 'r' - reply

also of classes have more 2 fields this. defining constants in class can messy in these situations.

so i'm trying implement values as

public class outgoingmessage {     private char action;      public final class actiontypes {         public static final char do_not_print = '0';         public static final char print = '1';         ...

and using below

... message.setaction(outgoingmessage.actiontypes.do_not_print); ... message.setfoobar(outgoingmessage.foobartypes.foo_bar); ...

what think? there wrong approach? how define these constants in library?

thanks lot

use enums in preference int or char constants:

public enum action {     donotprint,     print,     printandforward,     printandreply,     forward,     reply }  public class outgoingmessage {      private action action;

if need associate char action, this:

public enum action {     donotprint('0'),     print('1'),     printandforward('2'),     printandreply('3'),     forward('f'),     reply('r');      private static map<character, action> map = new hashmap<character, action>() {{         (action action : action.values()) {             put(action.getchar(), action);         }     }};      private final char c;      private action(char c) {         this.c = c;     }      public char getchar() {         return c;     }      public static action parse(char c) {         if (!mapholder.map.containskey(c))             throw new illegalargumentexception("invalid char: " + c);         return mapholder.map.get(c);     } }

here's how can use parse method:

public static void main(string[] args) {     system.out.println(action.parse('2')); // "printandforward"     system.out.println(action.parse('x')); // throws illegalargumentexception }

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