如果我應用了1種以上的方法，我的整數計數器將不起作用

Question

我使用的是supplyCounter，它是一個全局變量，用於計算制造商為庫存生成新隨機數的次數。

public class test {

private static Random manufacturer;
private static ArrayList<Integer> ordersForFirstFit, stocksForFirstFit, ordersForBestFit, stocksForBestFit;
private static int supplyCounter = 0;

public test() {

}

public static void main(String[] args) 
{
    ordersForFirstFit = createCustomerOrders(1000);
    ordersForBestFit = ordersForFirstFit;// using same data as first fit for best fit
    stocksForFirstFit = createStockOfRope();
    stocksForBestFit = stocksForFirstFit;// using same data as first fit for best fit
    manufacturer = new Random();

    supplyCounter = 0;
    firstFitAlgorithm(stocksForFirstFit, ordersForFirstFit);
    //showCustomerOrders(ordersForFirstFit);//for testing and debugging
    //showStockOfRope(stocksForFirstFit);//for testing and debugging

    supplyCounter = 0;
    bestFitAlgorithm(stocksForBestFit, ordersForBestFit);
    //showCustomerOrders(ordersForBestFit);//for testing and debugging
    //showStockOfRope(stocksForBestFit);//for testing and debugging

}

public static ArrayList<Integer> createCustomerOrders(int n) {
    ArrayList<Integer> ropeOrder = new ArrayList<Integer>();
    Random randomOrders = new Random();
    for(int i = 0; i < n+1; i++) 
    {
        ropeOrder.add(randomOrders.nextInt(100)+1);// because the range include 0 but exclude 100, therefore +1
        //System.out.println("Rope Orders "+i+": "+ropeOrder.get(i));
    }
    return ropeOrder;
}

public static void showCustomerOrders(ArrayList<Integer> ropeOrder) {
    for(int i = 0; i < ropeOrder.size()-1; i++) 
    {
        System.out.println("Rope Orders "+i+": "+ropeOrder.get(i));
    }
}

public static ArrayList<Integer> createStockOfRope() {
    ArrayList<Integer> ropeStock = new ArrayList<Integer>();
    Random randomStocks = new Random();
    for(int i = 0; i < 6; i++) 
    {
        ropeStock.add(i,randomStocks.nextInt(100)+101);//for a range between 100 to 200
        //System.out.println("Rope(s) in Stock "+i+": "+ropeStock.get(i));
    }
    return ropeStock;
}

public static void showStockOfRope(ArrayList<Integer> ropeStock) {
    for(int i = 0; i < ropeStock.size()-1; i++) 
    {
        System.out.println("Rope(s) in Stock "+i+": "+ropeStock.get(i));
    }
}

public static void insertionSort(ArrayList<Integer> data) {
    //initialize variables
    int key = 0, j = 0;

    for(int i = 1; i < data.size(); i++)
    {
        key = data.get(i);
        j = i;
        while( (j>0)&&(key < data.get(j-1)) )
        {
            data.set(j, data.get(j-1));
            j = j-1;
        }           
        data.set(j, key);
    }
}


public static void firstFitAlgorithm(ArrayList<Integer> ropeStock, ArrayList<Integer> ropeOrder) {
    //int supplyCounter = 0;
    long begin = System.nanoTime();

    for(int i = 0; i < ropeOrder.size(); i++) 
    {
        int j = 0;
        while( ropeOrder.get(i) > ropeStock.get(j) )
        {
            if(j == ropeStock.size()-1)
            {
                ropeStock.add(j,manufacturer.nextInt(100)+101);//Buy a rope from manufacturer then put the rope to the stock
                supplyCounter++;
                //then check to see whether it fits the requirement, if not, do the previous step again
            }
            else
                j++;
        }

        if( ropeOrder.get(i) <= ropeStock.get(j) )
        {
            if(ropeStock.get(j) - ropeOrder.get(i) > 5)//Assume rope coils shorter than 5m are scrapped
            {   
                ropeStock.set(j, ropeStock.get(j) - ropeOrder.get(i));
                ropeOrder.set(i, 0);
            }
            else
            {
                ropeStock.remove(j);
                if(ropeStock.size() == 0)//when the last rope in stock is sold, buy a new coil of rope from manufacturer
                    ropeStock.add(manufacturer.nextInt(100)+101);
                supplyCounter++;
                ropeOrder.set(i, 0);
            }
        }
    }

    long total = System.nanoTime() - begin;
    System.out.println("The time spent for Firstfit is: "+total+" nanoSeconds");
    System.out.println("The number of rope supplied by manufacturer for Firstfit is: "+supplyCounter+" ropes");

}

public static void bestFitAlgorithm(ArrayList<Integer> ropeStock, ArrayList<Integer> ropeOrder) {
    //int supplyCounter = 0;
    long begin = System.nanoTime();

    insertionSort(ropeStock);
    insertionSort(ropeOrder);

    int j = 0;
    for(int i = 0; i < ropeOrder.size(); i++) 
    {

        while( ropeOrder.get(i) > ropeStock.get(j) )
        {
            if(j == ropeStock.size()-1)
            {
                ropeStock.add(manufacturer.nextInt(100)+101);//Buy a rope from manufacturer then put the rope to the stock
                insertionSort(ropeStock);//then check to see whether it fits the requirement, if not, do the previous step again
                j++;
                supplyCounter++;
            }
            else
                j++;
        }

        if( ropeOrder.get(i) <= ropeStock.get(j) )
        {
            if(ropeStock.get(j) - ropeOrder.get(i) > 5)//Assume rope coils shorter than 5m are scrapped
            {   
                ropeStock.set(j, ropeStock.get(j) - ropeOrder.get(i));
                insertionSort(ropeStock);
                ropeOrder.set(i, 0);
            }
            else
            {
                ropeStock.remove(j);
                if(ropeStock.size() == 0)//when the last rope in stock is sold, buy a new coil of rope from manufacturer
                    ropeStock.add(manufacturer.nextInt(100)+101);
                supplyCounter++;
                ropeOrder.set(i, 0);
            }
            j = 0;
        }
    }

    long total = System.nanoTime() - begin;
    System.out.println("The time spent for Bestfit is: "+total+" nanoSeconds");
    System.out.println("The number of rope supplied by manufacturer for Bestfit is: "+supplyCounter+" ropes");
}
}

輸出是

Firstfit花費的時間是：5009697 nanoSeconds
制造商為Firstfit提供的繩索數量是：649條繩索
Bestfit花費的時間是：5358148 nanoSeconds
制造商為Bestfit提供的繩索數量是：0條繩索

但是，如果我只運行bestfit算法，則計數器返回一個不為0的合理值

public static void main(String[] args) 
{
    ordersForFirstFit = createCustomerOrders(1000);
    ordersForBestFit = ordersForFirstFit;// using same data as first fit for best fit
    stocksForFirstFit = createStockOfRope();
    stocksForBestFit = stocksForFirstFit;// using same data as first fit for best fit
    manufacturer = new Random();

    supplyCounter = 0;
    bestFitAlgorithm(stocksForBestFit, ordersForBestFit);
}

結果：

Bestfit花費的時間是：31895376 nanoSeconds
制造商為Bestfit提供的繩索數量是：465根繩索

我也嘗試在方法內創建計數器而不是使用全局變量，但是得到了相同的結果。

有人知道發生了什么嗎？

Answer 1

您的問題是您正在兩種算法之間共享數據。

更改

ordersForBestFit = ordersForFirstFit;

至

ordersForBestFit = new ArrayList<Integer>(ordersForFirstFit);

並改變

stocksForBestFit = stocksForFirstFit;

至

stocksForBestFit = new ArrayList<Integer>(stocksForFirstFit);

ArrayList的內容將是相同的整數。 但是，當您在第一個算法中對列表進行排序時，它會影響ArrayList的狀態，這會給您的下一個算法帶來問題。 通過創建一個新的ArrayList並將其傳遞給第二個算法，可以避免第一個算法的副作用。