Question

我刚开始使用计算机科学（Java）大约5周前，我仍然无法创建方法。我被分配创建一个NFL统计类，然后创建一个方法来显示计算。一切顺利，直到我在测试类中调用我的方法。这里似乎缺少什么？

NFLPlayer CLASS（包含方法）：

private int touchdowns;
private int interceptions;
private int passingAttempts;
private int completedPasses;
private int passingYards;
private int runningYards;
private int recievingYards;
private int tackles;
private int sacks;


// Method for Quarterback rating
public double QBRating(int touchdowns, int passingAttempts, int completedPasses,
        int passingYards, int interceptions) {

        double a = (completedPasses / passingAttempts - 0.3) * 5;
        double b = (passingYards / passingAttempts - 3) * 0.25;
        double c = (touchdowns / passingAttempts) * 25;
        double d = 2.375 - (interceptions / passingAttempts * 25);
        double ratingQB = ((a + b + c + d) / 6) * 100;
        {
        return ratingQB;
        }   

}

现在这是我的测试课，我在显示计算时遇到了麻烦

class MyTest {
public static void main(String[] args) {

    NFLPlayer playerStats = new NFLPlayer();

    //Player1 finding quarterback rating
    int touchdowns = 2;
    int passingAttempts = 44;
    int passingYards = 285;
    int interceptions = 1;
    int completedPasses = 35;

    // Call QB rating method
    playerStats.QBRating(touchdowns, passingAttempts, completedPasses,
            passingYards, interceptions); 

    System.out.println(QBRating);
}

}

Answer 1

您可以为每个值提供NFLPlayer类私有字段，而不是将这么多int个参数（很容易混淆）传递给您的方法：

public class NFLPlayer {

    private final String name;

    private int touchdowns;
    private int passingAttempts;
    private int completedPasses;
    private int passingYards;
    private int interceptions;

    public NFLPlayer(String name) {
        this.name = name;
    }

    // Method names start with a lower case character in Java
    // The name should usually be an imperative 'do something' not a noun ('something')
    // although there are exceptions to this rule (for instance in fluent APIs)
    public double calculateQbRating() {                
        double a = (completedPasses / passingAttempts - 0.3) * 5.0;
        double b = (passingYards / passingAttempts - 3.0) * 0.25;            
        // an AritmeticException will occur if passingAttempts is zero
        double c = (touchdowns / passingAttempts) * 25.0;
        double d = 2.375 - (interceptions / passingAttempts * 25.0);
        return ((a + b + c + d) / 6.0) * 100.0;
    }       

    public String getName() {
        return  name;
    }

    // setter for the touchdowns field
    public void setTouchdowns(int value) {
        touchdowns = value;
    }

    // TODO: add other setters for each private field

    @Override
    public String toString() {
        return String.format("Player %s has QB rating %s", name, calculateQbRating());
    }
}

您的申请（这不称为测试）：

class NFLApplication {

    public static void main(String[] args) {      

            NFLPlayer playerStats = new NFLPlayer("johnson");    

            playerStats.setTouchdowns(2);
            playerStats.setPassingAttempts(44);
            playerStats.setPassingYards(285);
            playerStats.setInterceptions(1);
            playerStats.setCompletedPasses(35);

            double qbRating = playerStats.calculateQbRating();    

            System.out.println(qbRating);
        }
}

使用JUnit框架测试您的NFLPlayer类（默认情况下，JUnit通常包含在您的IDE中）：

public class NFLPlayerTest {

    // instance of the class-under-test
    private NFLPlayer instance;

    // set up method executed before each test case is run
    @Before
    public void setUp() {
        instance = new NFLPlayer(); 
    }

    @Test
    public void testCalculateQbRatingHappy() {
        // SETUP
        instance.setTouchdowns(2);
        instance.setPassingAttempts(44);
        instance.setPassingYards(285);
        instance.setInterceptions(1);
        instance.setCompletedPasses(35);

        // CALL
        double result = playerStats.calculateQbRating();  

        // VERIFY
        // assuming here the correct result is 42.41, I really don't know
        assertEquals(42.41, result);
    }

    @Test
    public void testCalculateQbRatingZeroPassingAttempts() {
        // SETUP
        // passingAttempts=0 is not handled gracefully by your logic (it causes an ArithmeticException )
        // you will probably want to fix this 
        instance.setPassingAttempts(0);

        // CALL
        double result = playerStats.calculateQbRating();  

        // VERIFY
        // assuming here that you will return 0 when passingAttempts=0
        assertEquals(0, result);
    }
}

此测试类应该放在测试源目录中（通常在yourproject/src/test/yourpackage/中）。它需要一些在IDE中易于解析的导入，因为默认情况下JUnit通常是可用的。

要运行测试，请右键单击它并选择“运行测试”，“测试文件”等内容，具体取决于您使用的IDE（IDE是Eclipse，NetBeans或IntelliJ等开发工具）。您应该看到一些测试输出，指示测试是否成功（绿色）或是否存在故障（红色）。进行此类测试很有用，因为它会强制您考虑您的设计并编写更好的代码。（可测试代码通常比难以测试的代码更好）并且因为它会警告您新的更改是否会导致现有代码中的错误（回归）。

编辑：

要创建两个具有不同统计数据的玩家，您必须创建两个实例（我添加了name字段，以便我们可以更轻松地区分玩家）：

NFLPlayer player1 = new NFLPlayer("adams");
NFLPlayer player2 = new NFLPlayer("jones");

并给他们各自的统计数据：

player1.setTouchdowns(2);
player1.setPassingAttempts(4);
player1.setPassingYards(6);
player1.setInterceptions(8);
player1.setCompletedPasses(10);

player2.setTouchdowns(1);
player2.setPassingAttempts(3);
player2.setPassingYards(5);
player2.setInterceptions(7);
player2.setCompletedPasses(9);

你甚至可以创建一个玩家列表：

List<NFLPlayer> players = new ArrayList<>();
players.add(player1);
players.add(player2);

然后你可以在一个循环中打印出所有玩家评级：

for(NFLPlayer player : players) {
    // this uses the `toString` method I added in NFLPlayer
    System.out.println(player);
}

Answer 2

你不应该在SOP中调用方法名称而不是System.out.println（playerStats.QBRating（touchdown，passingAttempts，completedPasses， passYards，interceptions））; 或覆盖类中的toString（）方法，并将方法调用分配给局部变量并打印该值。还使用一些框架（Junit）而不是编写存根

如何在另一个类中测试我的方法？

2 个答案: