jodd-core/src/main/java/jodd/util/ArraysUtil.java
public static double[] join(double[]... arrays) {
		if (arrays.length == 0) {
			return new double[0];
		}
		if (arrays.length == 1) {
			return arrays[0];
		}
		int length = 0;
		for (double[] array : arrays) {
			length += array.length;
		}
		double[] result = new double[length];
		length = 0;
		for (double[] array : arrays) {
			System.arraycopy(array, 0, result, length, array.length);
			length += array.length;
		}
		return result;
	}
public static double[] join(double[]... arrays) {
		if (arrays.length == 0) {
			return new double[0];
		}
		if (arrays.length == 1) {
			return arrays[0];
		}
		int length = 0;
		for (double[] array : arrays) {
			length += array.length;
		}
		double[] result = new double[length];
		length = 0;
		for (double[] array : arrays) {
			System.arraycopy(array, 0, result, length, array.length);
			length += array.length;
		}
		return result;
	}
Join <code>double</code> arrays.