toString方法用Java调用

Question

  

可能重复：
  Why is the toString() method being called when I print an object?

我在下面有这段代码。我使用Room Class 中的 toString方法了解除输出之外的所有其他内容。在 HotelMain 类中，我刚刚调用了酒店类中的 displayRooms Method 。但是，当我运行程序时，控制台中显示了toString输出。

如果我是正确的toString（）是对象中值的文本表示。但是，我不确定在哪里调用toString方法。

有人可以解决我的困境吗？谢谢。

酒店等级

public class Hotel {

private String hotelName;
private Room[] rooms;

public Hotel(String hotelName, int numberOfRooms) {
    this.hotelName = hotelName;
    this.rooms = new Room[numberOfRooms];
}

public void addRooms(Room room) {

    int position = -1;

    for (int i = 0; i < this.rooms.length; i++) {
        Room tempRoom = rooms[i];

        if (tempRoom == null) {
            position = i;
            break;
        }
    }

    if (position != -1) {
        rooms[position] = room;
        System.out.println("New room added at postion " + position);

    } else {
        System.out.println("Addition of room failed.");
    }
}

public void displayRooms() {

    System.out.println("The Hotel: " + this.hotelName + " has the following rooms.");

    for (int i = 0; i < this.rooms.length; i++) {
        Room tempRoom = rooms[i];
        if (tempRoom != null) {
            System.out.println(tempRoom);
        }
    }

}

房间类

public class Room {

private int roomNumber;
private int numberOfBeds;
private boolean smokingOrNonSmoking;

public Room() {

}

public Room(int roomNumber, int numberOfBeds, boolean smokingOrNonSmoking) {
    this.roomNumber = roomNumber;
    this.numberOfBeds = numberOfBeds;
    this.smokingOrNonSmoking = smokingOrNonSmoking;
}

@Override
public String toString() {
    return "Room [roomNumber=" + roomNumber + ", numberOfBeds="
            + numberOfBeds + ", smokingOrNonSmoking=" + smokingOrNonSmoking
            + "]";
}

}

Hotel Main

public class HotelMain {

public static void main(String[] args) {

Hotel hotel = new Hotel("MahaRani Chain of Hotels", 10);
Room room1 = new Room(4, 2, true);
Room room2 = new Room(2, 1, false);
Room room3 = new Room(6, 3, true);
Room room4 = new Room(6, 4, false);

hotel.addRooms(room1);
hotel.addRooms(room3);
hotel.addRooms(room4);
hotel.addRooms(room2);

hotel.displayRooms();

}

}

控制台

Answer 1

Room tempRoom = rooms[i];
if (tempRoom != null) {
    System.out.println(tempRoom);
}

您的displayRooms()方法中包含上述代码。它打印tempRoom，它是Room的引用，因此它会调用toString()类中的Room方法。

Answer 2

致电

System.out.println(tempRoom);

在toString()上自动调用Room的tempRoom方法。

Answer 3

在这一行

System.out.println(tempRoom);

这与

相同

 System.out.println(tempRoom.toString());

Answer 4

toString是Object类的特殊方法，此处为description：

  

返回对象的字符串表示形式。通常，toString方法返回一个“文本表示”此对象的字符串。结果应该是一个简洁但信息丰富的表示，便于人们阅读。建议所有子类都覆盖此方法。

当对象应转换为文本表示时，此方法广泛用于那些地方。当您将对象打印到PrintStream（在这种情况下为System.out）时，此流会调用toString将此对象转换为字符串。