InitializationOnDemand.java

import java.util.HashMap;
import java.util.Map;

public class InitializationOnDemand {
    private static class LazyHolder {
        private static final Map<String, String> instance = create();
        static {
            System.out.println("static{}");
            instance.put("foo", "bar");
        }
        private static Map<String, String> create() {
            System.out.println("create()");
            return new HashMap<String, String>();
        }
        public static Map<String, String> get() {
            System.out.println("get()");
            return instance;
        }
    }
    public static void main(String[] args) {
        System.out.println("main() 1");
        Map<String, String> instance = LazyHolder.get();
        System.out.println("main() 2");
    }
}

main() 1
create()
static{}
get()
main() 2