java - How does this class work or how can you use it? -

i fell on class looks this:

public final class databasetype{      public static final databasetype type_limited_text = new databasetype();     public static final databasetype type_unlimited_text = new databasetype();     public static final databasetype type_date = new databasetype();     public static final databasetype type_decimal = new databasetype();      private databasetype(){     }      public string tostring(){         return "databasetype";     } } 

i need set type want understand what's happening here , have no clue how class works. whatever variable use return empty databasetype, no information. wonder how can use of such class. maybe there name type of class?

basically, class lists 4 enumerable constants, can use in method signatures

public databasetype gettypeofdb(); 

in client code, you'll have type-safe way compare constants:

if (gettypeofdb() == databasetype.type_limited_text) {     dosomething(); } 

even though implementation seems bit clumsy, quite closely emulates java 5 enum, gimby pointed out in comments. ideas in design following:

• the constructor private, meaning public static final databasetype instances declared within class can exist
• the class final cannot work around above restriction adding more constants in subclass
• the constant fields in class have strong typing, i.e. not ints, instead databasetypes, helps eliminate bugs caused typos or "magic numbers" in client code

the modern way same using enum instead:

public enum databasetype {     type_limited_text, type_unlimited_text, type_date, type_decimal; }