java Byte.toString 方法与String.ValueOf(Byte)效率比较

        int times = 10000000;        Byte[] li = new Byte[times];        for (int i = 0; i < times; i++) {            li[i] = (byte) i;        }                long timeA = System.currentTimeMillis();        for (int i = 0; i < times; i++) {            li[i].toString();        }        long timeB = System.currentTimeMillis();        for (int i = 0; i < times; i++) {            String.valueOf(li[i]);        }        long timeC = System.currentTimeMillis();        System.out.PRintln("A方法耗时：" + (timeB - timeA));        System.out.println("B方法耗时：" + (timeC - timeB));        if (timeB - timeA > timeC - timeB) {            System.out.println("B方法好");        } else {            System.out.println("A方法好");        }            

执行结果：

A方法耗时：1303

B方法耗时：239

B方法好

String.valueOf(li[i]);

li[i] 为何变成Object了？不是应该调用String.valueOf(Byte) ?求高手指教