计算某一段程序消耗的内存和时间【Java】

    public static void main(String[] args) {
        Runtime r = Runtime.getRuntime();
        r.gc();//计算内存前先垃圾回收一次
        long start = System.currentTimeMillis();//开始Time
        long startMem = r.freeMemory(); // 开始Memory
        new String("1");//！！！！！被测的程序！！！！！
        long endMem =r.freeMemory(); // 末尾Memory
        long end = System.currentTimeMillis();//末尾Time
        //输出
        System.out.println("用时消耗: "+String.valueOf(end - start)+"ms");
        System.out.println("内存消耗: "+String.valueOf((startMem- endMem)/1024)+"KB");
    }