class ShiftAssignment extends AbstractPersistable implements Comparable<ShiftAssignment> {

    private static final Comparator<Shift> COMPARATOR = Comparator.comparing(Shift::getShiftDate)
            .thenComparing(a -> a.getShiftType().getStartTimeString())
            .thenComparing(a -> a.getShiftType().getEndTimeString());

    private Shift shift;
    private int indexInShift;

    public ShiftAssignment() {
    }

    public ShiftAssignment(long id, Shift shift, int indexInShift) {
        super(id);
        this.shift = shift;
        this.indexInShift = indexInShift;
    }

    // Planning variables: changes during planning, between score calculations.
    @PlanningVariable(strengthComparatorClass = EmployeeStrengthComparator.class)
    private Employee employee;

    public Shift getShift() {
        return shift;
    }

    public void setShift(Shift shift) {
        this.shift = shift;
    }

    public int getIndexInShift() {
        return indexInShift;
    }

    public void setIndexInShift(int indexInShift) {
        this.indexInShift = indexInShift;
    }

    public Employee getEmployee() {
        return employee;
    }

    public void setEmployee(Employee employee) {
        this.employee = employee;
    }

    // ************************************************************************
    // Complex methods
    // ************************************************************************

    @JsonIgnore
    public ShiftDate getShiftDate() {
        return shift.getShiftDate();
    }

    @JsonIgnore
    public ShiftType getShiftType() {
        return shift.getShiftType();
    }

    @JsonIgnore
    public int getShiftDateDayIndex() {
        return shift.getShiftDate().getDayIndex();
    }

    @JsonIgnore
    public DayOfWeek getShiftDateDayOfWeek() {
        return shift.getShiftDate().getDayOfWeek();
    }

    @JsonIgnore
    public Contract getContract() {
        if (employee == null) {
            return null;
        }
        return employee.getContract();
    }

    @JsonIgnore
    public boolean isWeekend() {<FILL_FUNCTION_BODY>}

    @JsonIgnore
    public int getWeekendSundayIndex() {
        return shift.getShiftDate().getWeekendSundayIndex();
    }

    @Override
    public String toString() {
        return shift.toString();
    }

    @Override
    public int compareTo(ShiftAssignment o) {
        return COMPARATOR.compare(shift, o.shift);
    }
}

        if (employee == null) {
            return false;
        }
        WeekendDefinition weekendDefinition = employee.getContract().getWeekendDefinition();
        DayOfWeek dayOfWeek = shift.getShiftDate().getDayOfWeek();
        return weekendDefinition.isWeekend(dayOfWeek);
    
<methods>public long getId() ,public java.lang.String toString() <variables>protected java.lang.Long id