Java自行车和自行车测试

Question

我有问题要写我的代码。这是一个代码，我必须创建一个对象类并使用另一个类对象运行它。这个程序叫做自行车和自行车。我得到了自行车程序(它已经写好了)，我只需要写自行车就可以使用自行车了。现在，问题是，我已经创建了两个对象，名为NiceBicycle和CoolBicycle。我需要将我的NiceBicycle名称更改为"Kenny McCormick，但我做不到。“对于我编写的命令行，我一直收到错误的信息" error :变量NiceBicycle可能没有初始化”。

//使用setOwnerName NiceBicycle.setOwnerName("Kenny McCormick");将所有者的名称更改为Kenny NiceBicycle.setOwnerName("Kenny McCormick");

我该怎么办？

总之，这是自行车代码，也是我根据指导员命令编写的自行车测试代码。感谢您的回复

bicycle.java

public class Bicycle
{

// Instance field
private String ownerName;
private int licenseNumber;

// Constructor
public Bicycle( String name, int license )
{
     ownerName = name;
     licenseNumber = license;
}

// Returns the name of this bicycle's owner
public String getOwnerName()
{
     return ownerName;
}

// Assigns the name of this bicycle's owner
public void setOwnerName( String name )
{
     ownerName = name;
}

// Returns the license number of this bicycle
public int getLicenseNumber()
{
     return licenseNumber;
}

// Assigns the license number of this bicycle
public void setLicenseNumber( int license ) 
{
     licenseNumber = license;
}

}

这是我写的bicycletest.java。

  public class BicycleTest 
   {

    public static void main( String[] args )
    {

    // Create 1 Bicycle reference variable. For example: myBike
    Bicycle NiceBicycle;

    // Create 1 String reference variable for the owner's name
    String name;

    // Create 1 integer variable for license number
    int licenceNumber;

    // Assign your full name and a license number to the String and
    // integer variables
    name = "Boo Yeah";
    int licenseNumber = 9972;

    // Create a Bicycle object with the Bicycle class constructor
    // Use the variables you created as arguments to the constructor
    Bicycle CoolBicycle = new Bicycle( "Boo Yeah", 9972 );

    // Output the owner's name and license number in printf statements
    // using the object reference and the get methods.
    // For example: bike.getOwnerName()
    System.out.printf ("The CoolBicycle owner's name is %s\nThe license number is %d\n", CoolBicycle.getOwnerName(), CoolBicycle.getLicenseNumber());

    // Change the owner's name to Kenny McCormick using setOwnerName
    NiceBicycle.setOwnerName("Kenny McCormick");

    // Output the owner's name and license number in printf statements
      // using the Bicycle object reference variable and the get methods.
      System.out.printf ("The NiceBicycle owner's name is %s\n", NiceBicycle.getOwnerName());
 }

}

Answer 1

您需要在测试中实例化自行车并将其分配给NiceBicycle，方法是更改：

Bicycle NiceBicycle;

至：

Bicycle NiceBicycle = new Bicycle("", 0);

然后您可以对其进行setOwnerName()：

NiceBicycle.setOwnerName("Kenny McCormick");

另外，请注意，Java约定建议变量名以小写字母开头，因此，如果您想遵循约定，那么niceBicycle实际上应该是niceBicycle。

Answer 2

NiceBicycle尚未初始化(尚未创建自行车对象)。

试着替换

Bicycle NiceBicycle;

使用

Bicycle NiceBicycle = new Bicycle("",0);

Answer 3

编译器是仁慈的。在尝试使用NiceBicycle之前，您没有设置它。变量未设置。

还请注意，Java约定总是以小写开头的变量命名，以大写开头的类命名。这一点很重要，因为.负载过重，也就是说，它产生了许多不同的东西。