java - 无法从 HashSet 中的类调用方法

Question

我想做的是总结危险类别中的影响值

例如，它将遍历居住者列表，找到危险并从中获取影响量。然后将所有危险的总影响相加，并将该值返回给我。

下面有洞穴类、危险类和抽象居住者类。

当向洞穴添加危险时，它就会成为 HashSet 中的占用者。 当尝试使用 getImpact() 方法获取能量水平时，无法访问该方法，因为它是在 Hazard 而不是 Occupant 中。

我还有另外两个类也扩展了 Occupant。 玩家和元素。

在添加到 HashSet 时，我找不到将危险保留为 Hazard 类的方法，以便可以使用 getImpact() 方法。

在添加到 HashSet 时，这还需要满足其他类 Player 和 Item 的需要。

<小时/>

public class Cave {

HashSet<Occupant> occupants;
private double impact;

/**
 * Creat a new Cave instance with no occupants.
 */
public Cave() 
{
    occupants = new HashSet<Occupant>();
}

/**
 * Adds an occupant to a Cave if the occupant is not already there and
 * if cave currently has fewer than the maximum number of occupants.
 * @param occupant, the occupant to add
 * @return  true if successfully added
*/
public boolean addOccupant(Occupant occupant) {
    boolean validNewOccupant = occupant != null;
    boolean enoughRoom = occupants.size() < MAX_OCCUPANTS;
    if (validNewOccupant && enoughRoom) {
        validNewOccupant = occupants.add(occupant);
    }

    return validNewOccupant && enoughRoom;
}

/**
 * Gets the sum of the impact from all hazards in the cave
 * @returns hazardEnergyImpact
 */
public double getHazardEnergyImpacts(){
    double energyImpact = 0.0;
    for( Occupant occupant : occupants ){
        if(occupant.toString() == "!"){
            energyImpact += occupant.getImpact();
        }
    }
    return energyImpact;
}
}

<小时/>

public abstract class Occupant {

private Address address;
private String name;

/**
 * Construct an occupant for a known address & name.
 * @ param row, row of address  
 * @ param column, row of address.
 * @ param name, occupant's name
 */
public Occupant(Address address, String name) {
    this.address = address;
    this.name = name;
}

@Override
public String toString(){
    return "";
}
}

<小时/>

public class Hazard extends Occupant  {

private String longDescription;
private double impact;

/**
 * Construct a hazard with know attributes
 * @param row
 * @param column
 * @param name
 * @param longDescription
 * @param impact
 */
public Hazard(Address address, String name, String longDescription, double impact) {
    super(address, name);
    this.longDescription = longDescription;
    this.impact = impact;
}

@Override
public String toString(){
    return "!";
}

/**
 * gets impact amount
 * @returns impact
 */
public double getImpact(){
    return this.impact;
}
}

Answer 1

另一种选择是将 getImpact() 方法添加到 Occupant，例如，

public double getImpact() {
    return 0.0;
}

而 Hazard 的 @Override 实现的 getImpact() 只会将其 impact 实例变量返回为你已经设置好了。然后，您的循环被简化为:

public double getHazardEnergyImpacts() {
    double energyImpact = 0.0;
    for( Occupant occupant : occupants ) {
        energyImpact += occupant.getImpact();
    }
    return energyImpact;
}

如果您稍后需要提取到适当的接口(interface)抽象，现代 IDE 可以让这变得简单，这是件好事。