我需要在Java中连接两个字符串数组。

void f(String[] first, String[] second) {
    String[] both = ???
}

哪种方法最简单?


当前回答

你可以试试这个

 public static Object[] addTwoArray(Object[] objArr1, Object[] objArr2){
    int arr1Length = objArr1!=null && objArr1.length>0?objArr1.length:0;
    int arr2Length = objArr2!=null && objArr2.length>0?objArr2.length:0;
    Object[] resutlentArray = new Object[arr1Length+arr2Length]; 
    for(int i=0,j=0;i<resutlentArray.length;i++){
        if(i+1<=arr1Length){
            resutlentArray[i]=objArr1[i];
        }else{
            resutlentArray[i]=objArr2[j];
            j++;
        }
    }

    return resutlentArray;
}

你可以键入你的数组!!!

其他回答

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

both.toArray(new String[0]);

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});
    }

算法爱好者的另一个答案是:

public static String[] mergeArrays(String[] array1, String[] array2) {
    int totalSize = array1.length + array2.length; // Get total size
    String[] merged = new String[totalSize]; // Create new array
    // Loop over the total size
    for (int i = 0; i < totalSize; i++) {
        if (i < array1.length) // If the current position is less than the length of the first array, take value from first array
            merged[i] = array1[i]; // Position in first array is the current position

        else // If current position is equal or greater than the first array, take value from second array.
            merged[i] = array2[i - array1.length]; // Position in second array is current position minus length of first array.
    }

    return merged;

用法:

String[] array1str = new String[]{"a", "b", "c", "d"}; 
String[] array2str = new String[]{"e", "f", "g", "h", "i"};
String[] listTotalstr = mergeArrays(array1str, array2str);
System.out.println(Arrays.toString(listTotalstr));

结果:

[a, b, c, d, e, f, g, h, i]

在Java 8中使用流:

String[] both = Stream.concat(Arrays.stream(a), Arrays.stream(b))
                      .toArray(String[]::new);

或者像这样,使用flatMap:

String[] both = Stream.of(a, b).flatMap(Stream::of)
                      .toArray(String[]::new);

要对泛型类型执行此操作,必须使用反射:

@SuppressWarnings("unchecked")
T[] both = Stream.concat(Arrays.stream(a), Arrays.stream(b)).toArray(
    size -> (T[]) Array.newInstance(a.getClass().getComponentType(), size));
Object[] mixArray(String[] a, String[] b)
String[] s1 = a;
String[] s2 = b;
Object[] result;
List<String> input = new ArrayList<String>();
for (int i = 0; i < s1.length; i++)
{
    input.add(s1[i]);
}
for (int i = 0; i < s2.length; i++)
{
    input.add(s2[i]);
}
result = input.toArray();
return result;