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

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()]);
}

其他回答

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()]);
}

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));

我测试了以下代码,工作正常

我还使用了library:org.apache.mons.lang.ArrayUtils

public void testConcatArrayString(){
    String[] a = null;
    String[] b = null;
    String[] c = null;
    a = new String[] {"1","2","3","4","5"};
    b = new String[] {"A","B","C","D","E"};

    c = (String[]) ArrayUtils.addAll(a, b);
    if(c!=null){
        for(int i=0; i<c.length; i++){
            System.out.println("c[" + (i+1) + "] = " + c[i]);
        }
    }
}

当做

或者与心爱的瓜娃:

String[] both = ObjectArrays.concat(first, second, String.class);

此外,基元数组也有一些版本:

布尔型.凹形(第一个,第二个)字节.concat(第一,第二)字符凹面(第一个,第二个)双凹面(第一,第二)短裤.凹形(第一,第二)Ints.concat(第一,第二)长凹面(第一,第二)浮动凹面(第一,第二)

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。