SE450: Singleton: Often the singleton is public [20/32]

file:S.java [source] [doc-public] [doc-private]

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 package singleton.pub4; public abstract class S { private static S instance; static { if ("linux".equals(System.getProperty("os.name"))) instance = new SLinux(); else instance = new SOther(); } public static S get() {return instance;} public abstract int inc(); } final class SLinux extends S { private int i; public int inc() {return ++i;} } final class SOther extends S { private int i; public int inc() {return --i;} }

file:Main.java [source] [doc-public] [doc-private]

01 02 03 04 05 06 07 08 09 package singleton.pub4.main; import singleton.pub4.S; public class Main { public static void main (String[] args) { S s = S.get(); System.out.println(s.inc()); System.out.println(s.inc()); } }

You can also use a public method rather than a public field.