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

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});
    }

其他回答

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

both.toArray(new String[0]);
String [] both = new ArrayList<String>(){{addAll(Arrays.asList(first)); addAll(Arrays.asList(second));}}.toArray(new String[0]);

哇!这里有很多复杂的答案,包括一些依赖于外部依赖的简单答案。这样做怎么样:

String [] arg1 = new String{"a","b","c"};
String [] arg2 = new String{"x","y","z"};

ArrayList<String> temp = new ArrayList<String>();
temp.addAll(Arrays.asList(arg1));
temp.addAll(Arrays.asList(arg2));
String [] concatedArgs = temp.toArray(new String[arg1.length+arg2.length]);

如果您想在解决方案中使用ArrayList,可以尝试以下操作:

public final String [] f(final String [] first, final String [] second) {
    // Assuming non-null for brevity.
    final ArrayList<String> resultList = new ArrayList<String>(Arrays.asList(first));
    resultList.addAll(new ArrayList<String>(Arrays.asList(second)));
    return resultList.toArray(new String [resultList.size()]);
}

这是可行的,但您需要插入自己的错误检查。

public class StringConcatenate {

    public static void main(String[] args){

        // Create two arrays to concatenate and one array to hold both
        String[] arr1 = new String[]{"s","t","r","i","n","g"};
        String[] arr2 = new String[]{"s","t","r","i","n","g"};
        String[] arrBoth = new String[arr1.length+arr2.length];

        // Copy elements from first array into first part of new array
        for(int i = 0; i < arr1.length; i++){
            arrBoth[i] = arr1[i];
        }

        // Copy elements from second array into last part of new array
        for(int j = arr1.length;j < arrBoth.length;j++){
            arrBoth[j] = arr2[j-arr1.length];
        }

        // Print result
        for(int k = 0; k < arrBoth.length; k++){
            System.out.print(arrBoth[k]);
        }

        // Additional line to make your terminal look better at completion!
        System.out.println();
    }
}

它可能不是最有效的,但除了Java自己的API之外,它不依赖其他任何东西。