System类

【long begin = System.currentTimeMillis();】
for (int i = 0; i < 10000; i++) {
System.out.println(i);
}
long finish = System.currentTimeMillis();
long time = finish - begin;
//System.out.println("耗时：" + time + "毫秒");
int[] arr = {1,2,3,4,5,6,7};
int[] aee = {6,7,8,9,10,11};
【System.arraycopy(arr,0,aee,0, 3);】
【String s = Arrays.toString(aee);】
System.out.println(s);