Java - 尝试使用 get 方法打印字符串数组中的索引

Question

所以我有一个字符串数组

private  String[] transmission = {"Drive", "Park", "Reverse"};

这是我的set方法，我在练习我的switch语句，因为我不经常使用它。

public void setTransmission(String[] transmission) {
    System.out.println("To change the transmission, enter D for Drive,P for Park or R for reverse");
    switch (input.nextLine()) {
        case "D":
        case "d":
            System.out.println("The Car is currently in Drive.");
            transmission[0] = this.transmission[0];
            break;
        case "P":
        case "p":
            System.out.println("The Car is currently in Park.");
            transmission[1] = this.transmission[1];
            break;
        case "R":
        case "r":
            System.out.println("The Car is currently in Reverse");
            transmission[2] = this.transmission[2];
            break;

    } 

这是真正的问题。在我的 getMethod 中，它只打印数组中的第一个索引：

 public String getTransmission()
    {
        return String.format("The car is currently in %s",transmission);
    }

如何让它打印用户输入的内容？我知道我可以只使用字符串变量，但我更喜欢使用数组。

Answer 1

假设这发生在同一个类中，您需要将索引作为内部状态。

一个可能的实现是：

public class Car
{
    private final String[] transmission = { "Drive", "Park", "Reverse" };

    private final Scanner  input;

    private int            index;

    public Car( Scanner input )
    {
        this.input = input;
    }

    public void setTransmission()
    {
        System.out.println( "To change the transmission, enter D for Drive,P for Park or R for reverse" );
        switch ( input.nextLine() )
        {
        case "D":
        case "d":
            System.out.println( "The Car is currently in Drive." );
            index = 0;
            break;
        case "P":
        case "p":
            System.out.println( "The Car is currently in Park." );
            index = 1;
            break;
        case "R":
        case "r":
            System.out.println( "The Car is currently in Reverse" );
            index = 2;
            break;
        }
    }

    public String getTransmission()
    {
        return String.format( "The car is currently in %s", transmission[index] );
    }
}

如果您可以为您的问题添加更多上下文，这将有所帮助。尤其是您如何调用您的方法以及它们所在的位置。

更好的设计可能是为传输创建一个枚举并将解析与数据分开。

这会将汽车简化为没有任何逻辑的数据容器：

public class Car
{
    public enum Transmission
    {
        Drive, Park, Reverse
    }

    private Transmission transmission;

    public void setTransmission( Transmission transmission )
    {
        this.transmission = transmission;
    }

    public String getTransmission()
    {
        return String.format( "The car is currently in %s", transmission );
    }
}

使用这个 Car 类的应用程序会解析传输并在汽车中设置类型化的传输：

public class CarApplication
{
    public static void main( String[] args )
    {
        try ( Scanner input = new Scanner( System.in ) )
        {
            System.out.println( "To change the transmission, enter D for Drive,P for Park or R for reverse" );
            String answer = input.nextLine();
            Transmission transmission = parseTransmission( answer );

            Car car = new Car();

            car.setTransmission( transmission );

            System.out.println( car.getTransmission() );
        }
    }

    private static Transmission parseTransmission( String input )
    {
        switch ( input )
        {
        case "D":
        case "d":
            return Transmission.Drive;
        case "P":
        case "p":
            return Transmission.Park;
        case "R":
        case "r":
            return Transmission.Reverse;
        default:
            throw new IllegalArgumentException( "expected an input D,P,R but got: " + input );
        }
    }
}