StringBuffer和StringBuilder使用和方法

  //默认16个长度char[]存储如果传入字符串则str.length+16
        StringBuffer sb = new StringBuffer();
        //添加功能
        StringBuffer append = sb.append("a");
        //删除元素
        StringBuffer delete = sb.delete(1, 2);
        //删除单个字符
        StringBuffer stringBuffer = sb.deleteCharAt(1);
        //改
        StringBuffer asd = sb.replace(1, 2, "asd");
        sb.setCharAt(0,‘m‘);
        //插入
        StringBuffer zxcv = sb.insert(1, "zxcv");
        //倒转
        StringBuffer reverse = sb.reverse();
        //查找首次出现
        int zx = sb.indexOf("zx");
        //截取
        String substring = sb.substring(1, 2);
        //获取字符
        char charAt = sb.charAt(1);