将array转成list，然后直接add，再转回array，比arraycopy速度更快

import java.util.*;
 
public class Test {
    public static void main(String args[]) {
            long startTime1 = System.currentTimeMillis();
        for(int i=0; i<100000; i++)
        {
                String[] names = new String[] {"A", "B", "C"};
                String[] extended = new String[5];
                extended[3] = "D";
                extended[4] = "E";
                System.arraycopy(names, 0, extended, 0, names.length);
        }
        long endTime1 = System.currentTimeMillis();
        System.out.println("arraycopy花费时间"+(endTime1-startTime1)+"毫秒");
        
        long startTime2 = System.currentTimeMillis();
        for(int i=0; i<100000; i++)
        {
                String[] names = new String[] {"A", "B", "C"};
                String[] extended = new String[5];
                ArrayList<String> list = new ArrayList<String>(Arrays.asList(names));
                list.add("D");
                list.add("E");
                list.toArray(extended);
        }
        long endTime2 = System.currentTimeMillis();
        System.out.println("list花费时间"+(endTime2-startTime2)+"毫秒");
    }
}

运行结果

arraycopy花费时间26毫秒
list花费时间28毫秒