java - 如何从枚举调用？

Question

我有一个用于枚举的java代码。

public enum TruckType{
    LIGHT, MEDIUM, HEAVY, SUPER_HEAVY, TRAILER;
}

现在我正在尝试从枚举中获取 MEDIUM。

public static void main (String[] args) {
    Truck truck1 = new Truck("John Brown","9764780493","GJ67745676","Blue", 2400000.0,2019,18,TruckType.MEDIUM);
}

这就是我所做的，但它不起作用。我该怎么做才能从枚举中获得 MEDIUM ？我得到一个空值返回。

这是我的卡车类与 TruckTypes

public class Truck extends Vehicle{
    private int wheelNo;
    public TruckType classification;

    public Truck(String ownername, String telephonenumber, String chassisNum, String color, double estimatedVal, int year,
                 int wheelNo,TruckType Classification)
    {
        super(ownername, telephonenumber,chassisNum, color, estimatedVal, year);
        this.wheelNo = wheelNo;
        this.classification = classification;

Answer 1

您的问题在于此处的构造函数参数:TruckType Classification

public Truck(String ownername, String telephonenumber, String chassisNum, String color, double estimatedVal, int year,
             int wheelNo, TruckType Classification) {
    super(ownername, telephonenumber,chassisNum, color, estimatedVal, year);
    this.wheelNo = wheelNo;
    this.classification = classification;

由于参数的大写，Java 会看到:

    this.classification = classification;

实际上是这样的:

    // remains null
    this.classification = this.classification;

解决方案是检查拼写/大写并将 TruckType Classification 更改为 TruckType Classification