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。