???????????????????????????????????????String???????????????????????????е????????????

??????????????????????????????java???????????????????????????????????????ò????????????????????????

????java???????棬??????????????????????????????????????????????е???????????????????????????????????????棬??????????String??????????????????

????????????????У???String??????в????????????????μ?????????????????и??????????name??????????????????????????????μ??????????????????????????????????????????????????????????????????????????????й??????????????????????????????String????????StringBuffer????StringBuilder??

????2??StringBuilder??StringBuffer:?????????

????????????????????????StringBuilder??StringBuffer??????????????????????????????3?????????????????????????????String?????????

public class Test{
   
     public static void main(String[] args) {
         StringBuilder sb = new StringBuilder("С??");
         System.out.println(System.identityHashCode(sb));
         sb.append("????????");
         System.out.println(System.identityHashCode(sb));
     }
 }

???????н????

???????StringBuilder??StringBuffer???????????????????

????????????????????StringBuffer??????????????StringBuffer????????????????????synchronized???η?????????????÷????????Ч???????????ж?????????￡???????StringBuilder??

????StringBuffer???????

????StringBuilder???????

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