Constant time array equality check in java

ct_array_compare.java

package ct;

public class CT {

    /**
     * Constant time array equals check.
     * If the lengths do not match the function returns false immediately.
     * @param a array A
     * @param b array B
     * @return true if arrays are equal on defined intervals
     */
    public static boolean isEqual(byte[] a, byte[] b) {
        if (a.length != b.length) {
            return false;
        }

        byte result = 0;
        for (byte i = 0; i < a.length; i++) {
            result |= (byte)(a[i] ^ b[i]);
        }
        return result == 0;
    }

    /**
     * Constant time array equals check.
     * Exception behavior consistent with
     * <a href="https://docs.oracle.com/javacard/3.0.5/api/javacard/framework/Util.html#arrayCompare(byte[],%20short,%20byte[],%20short,%20short)">Util.arrayCompare()</a>
     *
     * @param a array A
     * @param offsetA offset to start equal check from for array A
     * @param b array B
     * @param offsetB offset to start equal check from for array B
     * @param length length of the compared sequence
     * @return true if arrays are equal on defined intervals
     */
    public static boolean isEqual(byte[] a, short offsetA, byte[] b, short offsetB, short length) {
        if (a == null || b == null){
            throw new NullPointerException();
        }
        if (offsetA < 0 || offsetB < 0 || length < 0){
            throw new ArrayIndexOutOfBoundsException();
        }
        if ((short)(offsetA + length) > a.length || (short)(offsetB + length) > b.length) {
            throw new ArrayIndexOutOfBoundsException();
        }

        byte result = 0;
        for (byte i = 0; i < length; i++) {
            result |= (byte)(a[(short)(offsetA + i)] ^ b[(short)(offsetB + i)]);
        }
        return result == 0;
    }

}

Is it not necessary that we always check against dummy array and return false when lenghts are diffrent?