Java - 通過arraylist並輸出最高到最低的數字？

Question

有沒有辦法讓它，所以我可以排序通過一個ArrayList輸出最高的號碼與找到的最低號碼？我有辦法，現在是一個「shoppinglist」所設置的是這樣的：

public void addToBag(String anyItem, int anyUnits, double anyCost){ 
    int checkUnits = anyUnits; 
    double checkCost = anyCost; 
    if(checkUnits < 0 || checkCost < 0){ 
     System.out.println("You must enter a value equal to or greater than 0!"); 
    }else{ 
    shoppingBag.add(new Item(anyItem, anyUnits, anyCost)); 
} 
} 

和輸出僅輸出列表

public void calculateSalesReceipt(){ 
    System.out.println("Enter the sales tax percentage (ex. 0.08 for 8%) or type \"random\" for a random number: "); 
    double tax = keybd.nextDouble(); 
    if(tax < 0){ 
     System.out.println("You must enter a value equal to or greater than 0!"); 
    }else{ 
    getPricePreTax(); 
    total = total; 
    taxCost = total * tax; 
    finaltotal = total + taxCost; 
    System.out.println("Sales Receipt"); 
    System.out.println("-------------"); 
    for(Item currentProduct : shoppingBag){ 
     System.out.println(currentProduct.getName() + " - " + currentProduct.getUnits() + " units " + " - $" + currentProduct.getCost()); 
    } 
    System.out.println("Total cost: $" + total); 
    System.out.println("Total tax: $" + taxCost); 
    System.out.println("Total cost with tax: $" + finaltotal); 
    System.out.println("Do you have any coupons? Enter \"yes\" or \"no\""); 
    String answer = keybd.next(); 
    if(answer.equals("yes")){ 
       applyCoupon(); 
      }else if(answer.equals("no")){ 
      System.out.println("Thank you!"); 
     }else if(answer != "yes" || answer != "no"){ 
      System.out.println("Thank you!"); 
     } 
    System.out.println("Coupon discounts: $" + couponAmount); 
    System.out.println("Grand total: $" + (finaltotal-couponAmount)); 
} 
} 

謝謝！

編輯：

將這項工作？

public void getLargest(){ 
    for(Item currentProduct : shoppingBag){ 
     System.out.println(Collections.max()); 
    } 
} 

Answer 1

你可能想Collections.max()（和Collections.min()，分別）。如果你想要整個列表，你可能想要Collections.sort()。

Answer 2

使用Google Guava：

Function<Item, Double> itemCostFunction = new Function<Item, Double>() { 
    @Override public Double apply(Item item) { 
    return item.getCost(); 
    } 
}; 

List<Item> sortedItems = Ordering.natural().onResultOf(itemCostFunction).sortedCopy(shoppingBag); 

現在

Item biggest = Iterables.getLast(sortedItems); // costliest 
Item smallest = sortedItems.get(0); // cheapest 

Answer 3

你要什麼排序呢？成本？

您可以創建一個新的類; CostComparator執行Comparator<Item>，並比較Item s依賴於他們的價格。