java - 在另一个类中传递方法时类型不兼容

Question

当我使用另一个类中的这些方法时，我遇到了不兼容的类型错误，我应该返回给定年份的平均马力在指定范围内的所有汽车的数组。

这是我从另一个类返回数组列表的方法:

public ArrayList<Lamborghini> getCarsFromThisYear(int year){
    ArrayList<Lamborghini> fromYear = new ArrayList<Lamborghini>();

    for( Lamborghini c : inventory){
        if(c.getModelYear() == year){
            fromYear.add(c);
        }
    }

    if( fromYear.size() == ZERO){
        return new ArrayList<>();
    }
    return fromYear;
}

public Lamborghini[] getCarsWithHorsepowerRange(double lowHP, double highHP){
    int matches = ZERO;

    for (Lamborghini c : inventory){
        if(c.getHorsepower() >= lowHP && c.getHorsepower() <= highHP){
            matches++;
        }
    }
    Lamborghini[] horsepower = new Lamborghini[matches];
    int indexInArray = ZERO;
    for (Lamborghini c : inventory){
        if(c.getHorsepower() >= lowHP && c.getHorsepower() <= highHP){
            horsepower[indexInArray] = c;
            indexInArray++;
        }
    }
    return horsepower;
}

这是我正在处理的事情，我在调用时遇到错误:c.getCarsFromThisYear(modelYear) 和 (c.getCarsWithHorsepowerRange(lowHP, highHP)

public LamborghiniCarLot[] getAllCarLotsWithAverageHorsepowerInRangeForYear(int modelYear, double lowHP, double highHP){
    int matches = ZERO;

    for(LamborghiniCarLot c : carLots){
        if (c.getCarsFromThisYear(modelYear)){
            if(c.getCarsWithHorsepowerRange(lowHP, highHP)){
                matches++;
            }
        }
    }

    LamborghiniCarLot[] search = new LamborghiniCarLot[matches];
    int index = ZERO;

    for(LamborghiniCarLot c : carLots){
        search[index] = c;
        index++;
    }
}

Answer 1

以下方法存在许多问题:

  public ArrayList<Lamborghini> getCarsFromThisYear(int year){
    ArrayList<Lamborghini> fromYear = new ArrayList<Lamborghini>();

    for( Lamborghini c : inventory){
        if(c.getModelYear() == year){
            fromYear.add(c);
        }
    }

    if( fromYear.size() == ZERO){
        return new ArrayList<>();
    }
    return fromYear;
  }

• 返回List<Lamborghini>而不是ArrayList<Lamborghini>
• 当fromYear列表的大小为“零”时，仅返回您在方法第二行中实例化的数组列表。或者更改 ArrayList<>()至ArrayList<Laborghini>在你的if陈述。

这是我的建议:

public List<Lamborghini> getCarsFromThisYear(int year){
    List<Lamborghini> fromYear = new ArrayList<Lamborghini>();

    for( Lamborghini c : inventory){
        if(c.getModelYear() == year){
            fromYear.add(c);
        }
    }

    return fromYear;
  }

另一个问题是 if (c.getCarsFromThisYear(modelYear)) 。该方法返回 List<Lamborghini>但 if 语句期望 boolean值(value)。