setRead(isRead(unixNumeric));
        setWrite(isWrite(unixNumeric));
        setExecute(isExecute(unixNumeric));
    }

    @Override
    public void unix(String unixSymbolic) {
        setRead(isRead(unixSymbolic));
        setWrite(isWrite(unixSymbolic));
        setExecute(isExecute(unixSymbolic));
    }

    @Override
    public void unix(int unixNumeric) {

     * doesn't really make sense, it's more like a traverse permission; for example, a user
     * must have 'execute' access to the 'bin' directory in order to execute the 'ls' or 'cd' commands.
     */
    void setExecute(boolean execute);

    }

    @Override
    public boolean getRead() {
        return read;
    }

    @Override
    public boolean getWrite() {
        return write;
    }

    @Override
    public boolean getExecute() {
        return execute;
    }

     * doesn't really make sense, it's more like a traverse permission; for example, a user
     * must have 'execute' access to the 'bin' directory in order to execute the 'ls' or 'cd' commands.
     */
    boolean getExecute();

     * returned value is equivalent to one of the three octal digits.
     */
    protected int toUnixNumeric() {
        return (getRead() ? 4 : 0) + (getWrite() ? 2 : 0) + (getExecute() ? 1 : 0);
    }

    protected static boolean isRead(int unixNumeric) {
        return (unixNumeric & 4) >> 2 == 1;
    }

    protected static boolean isRead(String unixSymbolic) {

        assertEquals("READ permission incorrect", read, permission.getRead());
        assertEquals("WRITE permission incorrect", write, permission.getWrite());
        assertEquals("EXECUTE permission incorrect", execute, permission.getExecute());
    }

    private static void assertInvalidUnixPermission(String unixPermission, String errorMessage) {
        try {
            newUnixPermission(unixPermission).toUnixNumeric();