???????????δ??? ??

????public class Main {

????public static void perform(Song s) {

????s.sing();

????}

????}

????public interface Song { void sing(); }

????public class GangnamStyle implements Song {

????@Override

????public void sing() {

????System.out.println("Oppan gangnam style!");

????}

????}

????public class Baby implements Song {

????@Override

????public void sing() {

????System.out.println("And I was like baby?? baby?? baby?? oh");

????}

????}

????perform????????????????????Σ???ζ??????sing???????????????????????????????????????????????????????s???????????????????е????????????????????????????????????????????

?????????????????????perform????????????????????????????????95%??????????GangnamStyle??????????????JIT??????????????鷽???????????????????????????????????????? ???????Java??????????????

????public static void perform(Song s) {

????if (s fastnativeinstanceof GangnamStyle) {

????System.out.println("Oppan gangnam style!");

????} else {

????s.sing();

????}

????}

????????????????????????????????????????????sing???????????????????????????

????JIT?????????к???????????????????????????е??????????о??????????????е????JVM????????Щ???????

???????????JIT??Щ???????

????JIT??????????????????????;???????????????д????????????????????????д???е??Щ???????????д?????????JIT???????????????????????? ——????д??????????????

?????????JIT???????????????????????????о??????????????????????????????????к?????????д??????????????