用java写一个构造函数

Question

这是我需要做的事情

编写一个构造函数，该构造函数接受四个字段的参数、每个字段的 mutator 方法和每个字段的访问器方法。此外，编写一个实例方法来计算该库存项目的总值。您可以通过将 numberOnHand 乘以价格来计算总值，并将该值作为双精度值返回。

这个程序大部分已经被淘汰了，但我不知道如何让它成为它应该的样子。

这是给我的。

    public PetStoreInventory(String s, String d, int units, double p) {
    //your code goes here
}

public void setDescription( String s){
    //your code goes here
}

public void setDepartment( String d){
  //your code goes here
}

public void setUnitsOnHand ( int units){
    //your code goes here
}

public void setPrice ( double p ){
    //your code goes here
}

public String getDescription(){
    return "";  //so it compiles, you must change this
}

public String getDepartment(){
  return "";  //so it compiles, you must change this
}

public int getUnitsOnHand(){
    return 0;   //so it compiles, you must change this
}

public double getPrice(){
    return 0.0; //so it compiles, you must change this
}

public double calcTotalValue(){
    return 0.0; //so it compiles, you must change this
}

这个输出来自的程序已经制作好了

Answer 1

您需要为四个字段添加实例变量，然后在代码中使用它们。因此，在构造函数中，您将设置这些实例变量的值（这些值通常会从另一个类发送到构造函数）。

private String description;
private String dept;
private int units;
private double price;

public PetStoreInventory(String s, String d, int units, double p) {
    this.description = s;
    this.dept = d;
    this.units = units;
    this.price = p;
}

public void setDescription( String s){
    // set instance var equal to the passed parameter
    this.description = s; 
}

public void setDepartment( String d){
    this.dept = d;
}

public void setUnitsOnHand ( int units){
    this.units = units;
}

public void setPrice ( double p ){
    this.price = p;
}

public String getDescription(){
    return description;  // return the instance var
}

public String getDepartment(){
   return dept; 
}

public int getUnitsOnHand(){
   return units;   
}

public double getPrice(){
   return price; 
}

public double calcTotalValue(){
   double totalVal = 0.0; //initalise a new variable

   /* the next line must calculate the total using the instance
      variables created at the beginning.
    */
   totalVal =?? //to be completed as it is an assignment

   return totalVal;
}

只有“totalVal = ??”这行需要完成。关注问题并使用实例变量，如果您需要更多帮助，请告诉我！

Answer 2

请注意，在您查看此解决方案并尝试自己解决问题后，我们建议您从错误中吸取教训并通过培训进行学习。 为了大家的理解，我尽量简化了

public class PetStoreInventory {
private String description;
private String department;
private int unitsOnHand;
private double price;
private double totalValue;
public PetStoreInventory(String description, String department,int unitsOnHand, double price){
        this.description = description;
        this.department = department;
        this.unitsOnHand = unitsOnHand;
        this.price = price;
    }

    public double calculateTotalValue(){
        return unitsOnHand*price;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }
    public String getDepartment() {
        return department;
    }
    public void setDepartment(String department) {
        this.department = department;
    }
    public int getUnitsOnHand() {
        return unitsOnHand;
    }
    public void setUnitsOnHand(int unitsOnHand) {
        this.unitsOnHand = unitsOnHand;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    public double getTotalValue() {
        return totalValue;
    }
    public void setTotalValue(double totalValue) {
        this.totalValue = totalValue;
    }

    public static void main(String[] args){
        PetStoreInventory item1 = new PetStoreInventory("Jack Russel", "Dogs", 4, 359.95);
        String description = item1.getDescription();
        String department = item1.getDepartment();
        int unitsOnHand = item1.getUnitsOnHand();
        double price = item1.getPrice();
        double totalValue = item1.calculateTotalValue();

        System.out.println(description + "\t" + department + "\t" + unitsOnHand + "\t" +price  + "\t" + totalValue);

    }
} 

结果例如：

Jack Russel    Dogs    4   359.95    1439.8