Java - 여러 배열을 하나로 합치기

import java.lang.reflect.Array;
import java.util.Arrays;

public class JoinArrays {

    public static void main(String[] args) {

        String[] arr1 = {"a", "b", "c", "d", "e"};
        String[] arr2 = {"1", "2", "3", "4", "5"};

        String[] result = joinArrays(arr1, arr2);

        System.out.println(Arrays.asList(result));
    }

    public static String[] joinArrays(String[]... arrays) {
        int len = 0;
        for (String[] array : arrays) {
            len += array.length;
        }

        String[] result = (String[]) Array.newInstance(String.class, len);

        int offset = 0;
        for (String[] array : arrays) {
            System.arraycopy(array, 0, result, offset, array.length);
            offset += array.length;
        }

        return result;
    }
}

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import org.apache.commons.lang3.ArrayUtils;

import java.util.Arrays;

public class JoinArrays2 {

    public static void main(String[] args) {

        String[] arr1 = {"a", "b", "c", "d", "e"};
        String[] arr2 = {"1", "2", "3", "4", "5"};

        String[] result = ArrayUtils.addAll(arr1, arr2);

        System.out.println(Arrays.asList(result));
    }
}

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dependencies {
    compile group: 'org.apache.commons', name: 'commons-lang3', version: '3.11'
    ...
}

import java.util.Arrays;
import java.util.stream.Stream;

public class JoinArrays3 {

    public static void main(String[] args) {

        String[] arr1 = {"a", "b", "c", "d", "e"};
        String[] arr2 = {"1", "2", "3", "4", "5"};

        String[] result = Stream.of(arr1, arr2).flatMap(Stream::of).toArray(String[]::new);

        System.out.println(Arrays.asList(result));
    }
}

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