????????д???????????κ???????????????????16???????????????????????????????????30???????????д??????????г??????????StringBuffer??λ??java.lang???????У??????????????????????????????

?????????????StringBuffer?????????????StringBuffer????????????????????????????append????????????????StringBuffer??????????β???????????????append??????????

????StringBuffer sb=new StringBuffer();
????
????sb.append(“B”);
????
????sb.append(“u”);
????
????sb.append(“i”);
????
????sb.append(“l”);
????
????sb.append(“d”);
????
????sb.append(“e”);
????
????sb.append(“r”);
????
????sb.append(“.com”);
????
????System.out.println(sb.toString());

??????Щ????????Builder.com???????????????????????????????????????????????String??????????????????????????????StringBuffer???toString??????????????????????????????????????????????????????????????????????????????????洢??

????append??????????????????????????????????????????????β??StringBuffer?????????????????????????

????StringBuffer??????

???????????capacity??length???????趨??????????????capacity??????????????????????????棩????????????????????????????????????length??????????????洢????????????????setLength???????????????????????????????????ensureCapacity???????????????????????С???????????????????????κ????????????????????Щ??????

????StringBuffer sb=new StringBuffer();
????
????sb.ensureCapacity(40);
????
????sb.append(“Builder.com is awesome!”);
????
????Systrm.out.println(sb.toString());
????
????sb.setLength(11);
????
????Systrm.out.println(sb.toString());