System类

import cn.tom.learning.Array;

import java.util.ArrayList;
import java.util.Arrays;

public class System0 {
    public static void main(String[] args) {
        long l = System.currentTimeMillis();
        System.out.println(l);
        int[]arr1={1,2,3,4,5,6};
        System.out.println(Arrays.toString(arr1));//遍历数组
        int[]arr2={9,8,7,6,5,4};
        System.arraycopy(arr1,0,arr2,2,3);//复制
        for (int i = 0; i < arr2.length; i++) {
            System.out.print(arr2[i]);

        }
    }
}