如何合計ArrayList中所有對象的總成本？

Question

Print all boats 
Color= blue Length= 22 Engine size= 60 Price= $12,800.00 
Color= white Length= 18 Num of Sails= 1 Price= $20,000.00 
Color= red Length= 42 Num of Sails= 3 Price= $48,000.00 
Color= yellow Length= 35 Engine size= 80 Price= $17,100.00 
Color= red Length= 50 Engine size= 120 Price= $22,400.00 
Color= blue Length= 33 Num of Sails= 2 Price= $37,000.00 
Color= white Length= 14 Engine size= 10 Price= $9,400.00 

Total price of all boats is $166,700.00. 

如何在ArrayList中獲得totalCost？

Most Expensive Boat: Color= red Length= 42 Num of Sails= Cost= $48,000.00 

如何獲得ArrayList以最高的成本搜索船？

我還沒有真正理解如何在ArrayList中獲得任何東西（除了只在一行代碼中重複打印），而沒有變量存在於測試類本身中。這是我使用的所有三個類的代碼。希望我能更好地瞭解你們如何獲得和使用任何東西（如計算，最高成本，低成本，最便宜等）。

船是繼承（超級） SailBoat和PowerBoat延伸船（子類） 清單（測試類）

public class Boat 
{ 
//attributes 
String color; //holds boat color 
int lengthBoat; //contains boat length 

//default constructor 
public Boat() 
{ 
    color = "white"; 
    lengthBoat = 0; 
} 
//parameterized constructor 
public Boat(String _color, int _lengthBoat) 
{ 
    setColor(_color); 
    setLengthBoat(_lengthBoat); 
} 
//mutator method for color 
public boolean setColor(String _color) 
{ 
    if(_color == "white" || _color == "red" || _color == "yellow" || _color == "blue") 
    { 
     color = _color; 
     return true; 
    } 
    else 
    { 
     System.out.println("ERROR - The color must be one of these following choices, \"white\", \"red\", \"yellow\", or \"blue\"."); 
     return false; 
    } 
} 
//accessor method for color 
public String getColor() 
{ 
    return color; 
} 
//mutator method for lengthBoat 
public boolean setLengthBoat(int _lengthBoat) 
{ 
    if(_lengthBoat >= 0 && _lengthBoat <= 50) 
    { 
     lengthBoat = _lengthBoat; 
     return true; 
    } 
    else 
    { 
     System.out.println("ERROR - The length must be between 0 and 50 inclusively."); 
     return false; 
    } 
} 
//accessor method for lengthBoat 
public int getLengthBoat() 
{ 
    return lengthBoat; 
} 
//toString method for printing results 
public String toString() 
{ 
    return "Color= " + getColor() + " Length= " + getLengthBoat(); 
} 
} 

帆船類

import java.text.NumberFormat; 

public class SailBoat extends Boat 
{ 
//attribute 
int numOfSails; //holds the number of Sails 

//default constructor 
public SailBoat() 
{ 
    numOfSails = 1; 
} 
//parameterized constructor 
public SailBoat(String _color, int _lengthBoat, int _numOfSails) 
{ 
    super(_color, _lengthBoat);//taken from the parent and inherited to be recognized in this class's constructor 
    setNumOfSails(_numOfSails); 
} 

//mutator method for numOfSails 
public boolean setNumOfSails(int _numOfSails) 
{ 
    if(_numOfSails >= 1 && _numOfSails <= 4) 
    { 
     numOfSails = _numOfSails; 
     return true; 
    } 
    else 
    { 
     System.out.println("ERROR - The number of sails must be between 1 and 4 inclusively."); 
     return false; 
    } 
} 
//accessor method for numOfSails 
public int getNumOfSails() 
{ 
    return numOfSails; 
} 
//calculates the price of the SailBoat as follows: 
public int calcPrice() 
{ 
    return lengthBoat * 1000 + getNumOfSails() * 2000; 
} 
//toString method 
public String toString() 
{ 
    NumberFormat nf = NumberFormat.getCurrencyInstance();//use to make the numbers as currency with $ automatically added 
    nf.setMinimumFractionDigits(2);//decimal is moved over 2 places 
    nf.setMaximumFractionDigits(2);//decimal is moved over 2 places 
    return super.toString() + " Num of Sails= " + getNumOfSails() + " Price= " + nf.format(calcPrice()); 
} 
//get the total Cost of all boats printed in arraylist 
public int getTotalCost() 
{ 
    int totalCost = 0; 
    totalCost += calcPrice();//as calcPrice() is printed, it is therefore added/updated to totalCost 
    return totalCost; 
} 
} 

摩托艇類

import java.text.NumberFormat; 

public class PowerBoat extends Boat 
{ 
//attributes 
int sizeOfEngine; //holds the engine size 

//default constructor 
public PowerBoat() 
{ 
    sizeOfEngine = 5; 
} 
//parameterized constructor 
public PowerBoat(String _color, int _lengthBoat, int _sizeOfEngine) 
{ 
    super(_color, _lengthBoat); 
    setSizeOfEngine(_sizeOfEngine); 
} 
//mutator method for sizeOfEngine 
public boolean setSizeOfEngine(int _sizeOfEngine) 
{ 
    if(_sizeOfEngine >= 1 && _sizeOfEngine <= 350) 
    { 
     sizeOfEngine = _sizeOfEngine; 
     return true; 
    } 
    else 
    { 
     System.out.println("ERROR - The size of Engine must be between 1 to 350 inclusively."); 
     return false; 
    } 
} 
//accessor for sizeOfEngine 
public int getSizeOfEngine() 
{ 
    return sizeOfEngine; 
} 
//caculates the price of the PowerBoat as follows: 
public int calcPrice() 
{ 
    return 5000 + lengthBoat * 300 + getSizeOfEngine() * 20; 
} 
//toString method for printing the results 
public String toString() 
{ 
    NumberFormat nf = NumberFormat.getCurrencyInstance(); //formats all the numbers a currency 
    nf.setMinimumFractionDigits(2); //sets the decimal place as a currency 
    nf.setMaximumFractionDigits(2); //sets the decimal place as a currency 
    return super.toString() + " Engine size= " + getSizeOfEngine() + " Price= " + nf.format(calcPrice()); 
} 
//get the total Cost of all boats printed in arraylist 
public int getTotalCost() 
{ 
    int totalCost = 0; 
    totalCost += calcPrice();//as calcPrice() is printed, it is therefore added/updated to totalCost 
    return totalCost; 
} 
} 

庫存

import java.util.ArrayList; 

public class Inventory 
{ 
    public static void main(String [] args) 
    { 
    //boat objects 
    Boat pb1 = new PowerBoat("blue", 22, 60); 
    Boat sb1 = new SailBoat("white", 18, 1); 
    Boat sb2 = new SailBoat("red", 42, 3); 
    Boat pb2 = new PowerBoat("yellow",35, 80); 
    Boat pb3 = new PowerBoat("red", 50, 120); 
    Boat sb3 = new SailBoat("blue", 33, 2); 
    Boat pb4 = new PowerBoat("white", 14, 10); 

    ArrayList<Boat> AL = new ArrayList<Boat>(); 
    //add boat objects to arraylist 
    AL.add(pb1); 
    AL.add(sb1); 
    AL.add(sb2); 
    AL.add(pb2); 
    AL.add(pb3); 
    AL.add(sb3); 
    AL.add(pb4); 

    //print all boat objects 
    System.out.println("Print all boats"); 
    for(Boat anyBoat : AL) 
    { 
     System.out.println(anyBoat.toString()); 
     //System.out.println("Total price of all boats is " + anyBoat.getTotalCost()); 
    } 
    } 
} 

Answer 1

int sumCost = 0; 
for(Boat b : AL) 
{ 
    sumCost += b.calcPrice(); 
} 
return sumCost; 

Answer 2

「我怎麼在TOTALCOST ArrayList的？」
AND
「我如何獲得ArrayList以最高的成本搜索船？」
答：

int max = 0; 
int totalcost = 0; 
Boat mostExpensiveBoat = null; 
for (Boat anyBoat : AL) 
{ 
    if (anyBoat instanceof SailBoat) { 
     totalcost += anyBoat.calcPrice(); 
     if (anyBoat.calcPrice() > max) { 
      max = anyBoat.calcPrice(); 
      mostExpensiveBoat = anyBoat; 
     } 
    } 
}  
// if not null print out most expensive boat here 

注意：如果你想以滿足潛在相同的最高價使用數組列表保存最昂貴的船/ s的船隻。