您可以尝试连接多个数组的方法：

public static <T> T[] concatMultipleArrays(T[]... arrays)
{
   int length = 0;
   for (T[] array : arrays)
   {
      length += array.length;
   }
   T[] result = (T[]) Array.newInstance(arrays.getClass().getComponentType(), length) ;

   length = 0;
   for (int i = 0; i < arrays.length; i++)
   {
      System.arraycopy(arrays[i], 0, result, length, arrays[i].length);
      length += arrays[i].length;
   }

   return result;
}

ArrayList<String> both = new ArrayList(Arrays.asList(first));
both.addAll(Arrays.asList(second));

both.toArray(new String[0]);

应该会成功的。这是假设String[]第一个，String[]第二个

List<String> myList = new ArrayList<String>(Arrays.asList(first));
myList.addAll(new ArrayList<String>(Arrays.asList(second)));
String[] both = myList.toArray(new String[myList.size()]);

只是想添加，您也可以使用System.arraycopy：

import static java.lang.System.out;
import static java.lang.System.arraycopy;
import java.lang.reflect.Array;
class Playground {
    @SuppressWarnings("unchecked")
    public static <T>T[] combineArrays(T[] a1, T[] a2) {
        T[] result = (T[]) Array.newInstance(a1.getClass().getComponentType(), a1.length+a2.length);
        arraycopy(a1,0,result,0,a1.length);
        arraycopy(a2,0,result,a1.length,a2.length);
        return result;
    }
    public static void main(String[ ] args) {
        String monthsString = "JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC";
        String[] months = monthsString.split("(?<=\\G.{3})");
        String daysString = "SUNMONTUEWEDTHUFRISAT";
        String[] days = daysString.split("(?<=\\G.{3})");
        for (String m : months) {
            out.println(m);
        }
        out.println("===");
         for (String d : days) {
            out.println(d);
        }
        out.println("===");
        String[] results = combineArrays(months, days);
        for (String r : results) {
            out.println(r);
        }
        out.println("===");
    }
}

我使用下一个方法使用java8连接任意数量的相同类型的数组：

public static <G> G[] concatenate(IntFunction<G[]> generator, G[] ... arrays) {
    int len = arrays.length;
    if (len == 0) {
        return generator.apply(0);
    } else if (len == 1) {
        return arrays[0];
    }
    int pos = 0;
    Stream<G> result = Stream.concat(Arrays.stream(arrays[pos]), Arrays.stream(arrays[++pos]));
    while (pos < len - 1) {
        result = Stream.concat(result, Arrays.stream(arrays[++pos]));
    }
    return result.toArray(generator);
}

用法：

 concatenate(String[]::new, new String[]{"one"}, new String[]{"two"}, new String[]{"three"}) 

or

 concatenate(Integer[]::new, new Integer[]{1}, new Integer[]{2}, new Integer[]{3})

在Java 8中

public String[] concat(String[] arr1, String[] arr2){
    Stream<String> stream1 = Stream.of(arr1);
    Stream<String> stream2 = Stream.of(arr2);
    Stream<String> stream = Stream.concat(stream1, stream2);
    return Arrays.toString(stream.toArray(String[]::new));
}