Java面向对象：解决构造器中创建对象的外部访问问题

public class Bus
{
    // ... 其他实例变量 ...

    public Bus(int tripNumber)
    {
        this.tripNumber = tripNumber;

        if (tripNumber==1)
        {
            // trip1 在此处被声明为局部变量
            Trip trip1 = new Trip(this, tripNumber);
        }
    }
    // ... 其他方法 ...
}

public class Bus
{
    private int tripNumber;
    private String model;
    private String type;
    private int age;
    private int capacity;
    private int remainingCapacity;
    private boolean[][] seats;
    private Trip assignedTrip; // 声明为实例变量

    // ... 构造器和方法 ...
}

public class Bus
{
    // ... 其他实例变量 ...
    private Trip assignedTrip; // 声明为实例变量

    public Bus(int tripNumber)
    {
        this.tripNumber = tripNumber;

        if (tripNumber==1)
        {
            this.model = "Setra";
            this.type = "2+2";
            this.age = 8;
            this.capacity = 40;
            this.remainingCapacity = 23;

            // 将创建的Trip对象赋值给实例变量
            this.assignedTrip = new Trip(this, tripNumber);
        }
    }
    // ... toString() 方法 ...
}

public class Bus
{
    // ... 其他实例变量 ...
    private Trip assignedTrip; // 声明为实例变量

    public Bus(int tripNumber)
    {
        // ... 构造器逻辑 ...
        if (tripNumber==1)
        {
            // ... 初始化Bus属性 ...
            this.assignedTrip = new Trip(this, tripNumber);
        }
    }

    // 提供一个公共的Getter方法来获取Trip对象
    public Trip getAssignedTrip() {
        return assignedTrip;
    }

    public String toString()
    {
        return ("\n\tBus Information:\n\t\tBus: " + this.model + "\n\t\tType: " + this.type + "\n\t\tAge: " + this.age + "\n\t\tCapacity" + this.capacity + "\n\t\tRemainingCapacity" + this.remainingCapacity);
    }
}

public class Interface
{
    public static void main(String args[])
    {
        Bus bus1 = new Bus(1);
        // 通过Bus实例的Getter方法获取Trip对象并调用其toString()
        if (bus1.getAssignedTrip() != null) { // 检查是否已分配行程
            System.out.println(bus1.getAssignedTrip().toString());
        } else {
            System.out.println("No trip assigned for bus1.");
        }
    }
}

public class Bus
{
    private int tripNumber;
    private String model;
    private String type;
    private int age;
    private int capacity;
    private int remainingCapacity;
    private boolean[][] seats;
    private Trip assignedTrip; // 声明为实例变量

    public Bus(int tripNumber)
    {
        this.tripNumber = tripNumber;

        if (tripNumber == 1)
        {
            this.model = "Setra";
            this.type = "2+2";
            this.age = 8;
            this.capacity = 40;
            this.remainingCapacity = 23;

            // 将创建的Trip对象赋值给实例变量
            this.assignedTrip = new Trip(this, tripNumber);
        }
    }

    // 提供一个公共的Getter方法来获取Trip对象
    public Trip getAssignedTrip() {
        return assignedTrip;
    }

    @Override
    public String toString()
    {
        return ("\n\tBus Information:\n\t\tBus: " + this.model + "\n\t\tType: " + this.type + "\n\t\tAge: " + this.age + "\n\t\tCapacity: " + this.capacity + "\n\t\tRemainingCapacity: " + this.remainingCapacity);
    }
}

public class Trip
{
    private int tripNumber;
    private String date;
    private String origin;
    private String destination;
    private String departureTime;
    private String arrivalTime;
    private Bus assignedBus;

    public Trip(Bus bus, int tripNumber)
    {
        if (tripNumber == 1)
        {
            this.tripNumber = 1;
            this.assignedBus = bus;
            this.date = "27/11/2022";
            this.origin = "Ankara";
            this.destination = "Istanbul";
            this.departureTime = "00:15";
            this.arrivalTime = "06:30";
        }
    }

    @Override
    public String toString()
    {
        // 避免在toString中再次调用assignedBus.toString()导致无限递归或冗余信息
        // 可以选择性地打印部分Bus信息或只打印Trip信息
        return tripNumber + ") Trip Information: \n\tDate: " + this.date + "\n\tFrom: " + this.origin + " to " + this.destination + "\n\tTrip time: " + this.departureTime + " to " + this.arrivalTime;
        // 如果需要Bus信息，可以这样：
        // return tripNumber + ") Trip Information: \n\tDate: " + this.date + "\n\tFrom: " + this.origin + " to " + this.destination + "\n\tTrip time: " + this.departureTime + " to " + this.arrivalTime + "\n\tAssigned Bus Model: " + (assignedBus != null ? assignedBus.getModel() : "N/A");
    }

    // 如果需要在Trip的toString中获取Bus模型，Bus类需要提供getModel()方法
    // 例如在Bus类中添加:
    // public String getModel() { return this.model; }
}

public class Interface
{
    public static void main(String args[])
    {
        Bus bus1 = new Bus(1);

        // 通过Bus实例的Getter方法获取Trip对象并调用其toString()
        if (bus1.getAssignedTrip() != null) {
            System.out.println(bus1.getAssignedTrip().toString());
        } else {
            System.out.println("Bus 1 has no assigned trip for tripNumber 1.");
        }

        Bus bus2 = new Bus(2); // 假设tripNumber=2没有分配行程
        if (bus2.getAssignedTrip() != null) {
            System.out.println(bus2.getAssignedTrip().toString());
        } else {
            System.out.println("Bus 2 has no assigned trip for tripNumber 2.");
        }
    }
}