在Java中引用屬性的問題

Question

我一直在想如何正確地將這些屬性從數據類傳遞給可執行類，但是我不知道如何。這裏是數據類：

public class Motor { 
     private int cylinders; 
     private int hp; 
     private String type; 
     public Motor(int cylinders, int hp, String type) { 
      this.cylinders = cylinders; 
      this.hp = hp; 
      this.type = type; 
     } 
     public int getCylinders() { 
      return cylinders; 
     } 
     public int getHp() { 
      return hp; 
     } 
     public String getType() { 
      return type; 
     } 
     public String toString() { 
      return "Motor: cylinders=" + this.cylinders + ", hp=" + 
        this.hp + ", type=" + this.type; 
     } 
} 

現在，在另一個數據類中，我應該引用Motor並創建一堆其他屬性。我沒有與這一個任何（明顯的）錯誤，但我想沒有這將使任何意義，如果我沒有將它張貼：

public class Vehicle { 
     private String make; 
     private String model; 
     private int year; 
     private double price; 
     private Motor motor; 
     public Vehicle(String make, String model, int year, double price, Motor motor) { 
      this.make = make; 
      this.model = model; 
      this.year = year; 
      this.price = price; 
      this.motor = motor; 

     } 
    public double getPrice() { 
      return price; 
     } 
     public void setPrice(double price) { 
      this.price = price; 
     } 
     public String toString() { 
      return "Vehicle make=" + this.make + ", model=" + 
        this.model + ", year=" + this.year + 
        ", price=" + this.price + ", motor=" + 
        this.motor; 
     } 
    } 

這其中真正的問題是，當我創建了一個汽車對象TestVehicle我得到一個錯誤，當我嘗試從後在電機增加對汽缸，馬力和類型的值：

public class TestVehicle { 

    public static void main(String[] args) { 
     Vehicle v1 = new Vehicle("Toyota", "Corolla", 2015, 15999.0, 7, 300, "Gas"); 
     System.out.println(v1.toString()); 

    } 

} 

我得到的錯誤，當我試圖執行它： 異常線程「main 「java.lang.Error：未解決的編譯問題： 構造函數Vehicle（String，String，int，double，int，int，String）未定義

非常感謝！

Answer 1

Exception in thread "main" java.lang.Error: Unresolved compilation problem: The constructor Vehicle(String, String, int, double, int, int, String) is undefined

Vehicle v1 = new Vehicle("Toyota", "Corolla", 2015, 15999.0, 7, 300, "Gas"); 

變化

Motor motor = new Motor(7, 300, "Gas"); 
Vehicle v1 = new Vehicle("Toyota", "Corolla", 2015, 15999.0, motor); 

檢查構造函數。

Answer 2

Vehicle的Parameter傳遞構造函數存在一些問題。請嘗試下面的代碼，它工作正常

class Motor { 
     private int cylinders; 
     private int hp; 
     private String type; 
     public Motor(int cylinders, int hp, String type) { 
      this.cylinders = cylinders; 
      this.hp = hp; 
      this.type = type; 
     } 
     public int getCylinders() { 
      return cylinders; 
     } 
     public int getHp() { 
      return hp; 
     } 
     public String getType() { 
      return type; 
     } 
     public String toString() { 
      return "Motor: cylinders=" + this.cylinders + ", hp=" + 
        this.hp + ", type=" + this.type; 
     } 
} 


class Vehicle { 
     private String make; 
     private String model; 
     private int year; 
     private double price; 
     private Motor motor; 
     public Vehicle(String make, String model, int year, double price, Motor motor) { 
      this.make = make; 
      this.model = model; 
      this.year = year; 
      this.price = price; 
      this.motor = motor; 

     } 
    public double getPrice() { 
      return price; 
     } 
     public void setPrice(double price) { 
      this.price = price; 
     } 
     public String toString() { 
      return "Vehicle make=" + this.make + ", model=" + 
        this.model + ", year=" + this.year + 
        ", price=" + this.price + ", motor=" + 
        this.motor; 
     } 
    } 

class TestVehicle { 

    public static void main(String[] args) { 
     Motor m1 = new Motor(7,300,"Gas"); 
     Vehicle v1 = new Vehicle("Toyota", "Corolla", 2015, 15999.0,m1); 
     System.out.println(v1.toString()); 

    } 

} 

Answer 3

這是你的構造函數，你期待字符串，字符串，整型，雙和汽車。

public Vehicle(String make, String model, int year, double price, Motor motor) { 
     this.make = make; 
     this.model = model; 
     this.year = year; 
     this.price = price; 
     this.motor = motor; 

    } 

您的汽車有一個構造函數，如：

public Motor(int cylinders, int hp, String type) { 
      this.cylinders = cylinders; 
      this.hp = hp; 
      this.type = type; 
     } 

所以，如果你想通過電機參數直接作爲INT，INT和字符串到車輛的構造需要車輛構造函數接受小號tring，String，int，double，int，int，字符串。

你可以在第二consturctor添加到您的車輛類，如：

public Vehicle(String make, String model, int year, double price, int cylinders, int hp, String type) { 
    this.make = make; 
    this.model = model; 
    this.year = year; 
    this.price = price; 
    this.motor = new Motor(cylinders, hp, type); 
} 

但是，這不是一個很好的風格，如果有新的變化你可能會忘記更改這兩個構造函數。更好地鏈接構造函數。

public Vehicle(String make, String model, int year, double price, int cylinders, int hp, String type) { 
     this.(make, model, year, price, new Motor(cylinders, hp, type)) 
    }