我看到许多带有公共静态T[]concat（T[]a，T[]b）｛｝等签名的通用答案，但据我所知，这些答案只适用于Object数组，而不适用于基元数组。下面的代码既适用于对象数组，也适用于基元数组，使其更通用。。。

public static <T> T concat(T a, T b) {
        //Handles both arrays of Objects and primitives! E.g., int[] out = concat(new int[]{6,7,8}, new int[]{9,10});
        //You get a compile error if argument(s) not same type as output. (int[] in example above)
        //You get a runtime error if output type is not an array, i.e., when you do something like: int out = concat(6,7);
        if (a == null && b == null) return null;
        if (a == null) return b;
        if (b == null) return a;
        final int aLen = Array.getLength(a);
        final int bLen = Array.getLength(b);
        if (aLen == 0) return b;
        if (bLen == 0) return a;
        //From here on we really need to concatenate!

        Class componentType = a.getClass().getComponentType();
        final T result = (T)Array.newInstance(componentType, aLen + bLen);
        System.arraycopy(a, 0, result, 0, aLen);
        System.arraycopy(b, 0, result, aLen, bLen);
        return result;
    }

    public static void main(String[] args) {
        String[] out1 = concat(new String[]{"aap", "monkey"}, new String[]{"rat"});
        int[] out2 = concat(new int[]{6,7,8}, new int[]{9,10});
    }

我发现我必须处理数组可以为空的情况。。。

private double[] concat  (double[]a,double[]b){
    if (a == null) return b;
    if (b == null) return a;
    double[] r = new double[a.length+b.length];
    System.arraycopy(a, 0, r, 0, a.length);
    System.arraycopy(b, 0, r, a.length, b.length);
    return r;

}
private double[] copyRest (double[]a, int start){
    if (a == null) return null;
    if (start > a.length)return null;
    double[]r = new double[a.length-start];
    System.arraycopy(a,start,r,0,a.length-start); 
    return r;
}

我看到许多带有公共静态T[]concat（T[]a，T[]b）｛｝等签名的通用答案，但据我所知，这些答案只适用于Object数组，而不适用于基元数组。下面的代码既适用于对象数组，也适用于基元数组，使其更通用。。。

public static <T> T concat(T a, T b) {
        //Handles both arrays of Objects and primitives! E.g., int[] out = concat(new int[]{6,7,8}, new int[]{9,10});
        //You get a compile error if argument(s) not same type as output. (int[] in example above)
        //You get a runtime error if output type is not an array, i.e., when you do something like: int out = concat(6,7);
        if (a == null && b == null) return null;
        if (a == null) return b;
        if (b == null) return a;
        final int aLen = Array.getLength(a);
        final int bLen = Array.getLength(b);
        if (aLen == 0) return b;
        if (bLen == 0) return a;
        //From here on we really need to concatenate!

        Class componentType = a.getClass().getComponentType();
        final T result = (T)Array.newInstance(componentType, aLen + bLen);
        System.arraycopy(a, 0, result, 0, aLen);
        System.arraycopy(b, 0, result, aLen, bLen);
        return result;
    }

    public static void main(String[] args) {
        String[] out1 = concat(new String[]{"aap", "monkey"}, new String[]{"rat"});
        int[] out2 = concat(new int[]{6,7,8}, new int[]{9,10});
    }

一个100%旧的java和没有System.arraycopy的解决方案（例如GWT客户端中不可用）：

static String[] concat(String[]... arrays) {
    int length = 0;
    for (String[] array : arrays) {
        length += array.length;
    }
    String[] result = new String[length];
    int pos = 0;
    for (String[] array : arrays) {
        for (String element : array) {
            result[pos] = element;
            pos++;
        }
    }
    return result;
}

仅使用Java自己的API：

String[] join(String[]... arrays) {
  // calculate size of target array
  int size = 0;
  for (String[] array : arrays) {
    size += array.length;
  }

  // create list of appropriate size
  java.util.List list = new java.util.ArrayList(size);

  // add arrays
  for (String[] array : arrays) {
    list.addAll(java.util.Arrays.asList(array));
  }

  // create and return final array
  return list.toArray(new String[size]);
}

现在，这段代码不是最有效的，但它只依赖于标准的java类，而且很容易理解。它适用于任意数量的String[]（甚至是零数组）。

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));
}