python 算法 Java 连接合并两个数组(Array)的五种方法

1、使用泛型方法和System.arraycopy实现

T可以是基础类型，也是类类型

public static T concatenate(T a, T b) {

if (!a.getClass().isArray() || !b.getClass().isArray()) {

throw new IllegalArgumentException();

}

Class resCompType;

Class aCompType = a.getClass().getComponentType();

Class bCompType = b.getClass().getComponentType();

if (aCompType.isAssignableFrom(bCompType)) {

resCompType = aCompType;

} else if (bCompType.isAssignableFrom(aCompType)) {

resCompType = bCompType;

} else {

throw new IllegalArgumentException();

}

int aLen = Array.getLength(a);

int bLen = Array.getLength(b);

@SuppressWarnings("unchecked")

T result = (T) Array.newInstance(resCompType, aLen + bLen);

System.arraycopy(a, 0, result, 0, aLen);

System.arraycopy(b, 0, result, aLen, bLen);

return result;

}

2、使用ArrayUtils.addAll实现

String[] both = (String[])ArrayUtils.addAll(first, second);

3、不使用System.arraycopy实现

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;

}

4、使用ObjectArrays.concat实现

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

5、使用Arrays.copyOf()实现

public static T[] concatAll(T[] first, T[]... rest) {

int totalLength = first.length;

for (T[] array : rest) {

totalLength += array.length;

}

T[] result = Arrays.copyOf(first, totalLength);

int offset = first.length;

for (T[] array : rest) {

System.arraycopy(array, 0, result, offset, array.length);

offset += array.length;

}

return result;

}

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