如何设置数组的内容等于第二个数组的内容

Question

我正在使用贪婪算法来计算变化，我想将我用过的硬币保存到新的aray中，但是我：

Exception in thread "main" java.lang.NullPointerException
    at lacy_lab_7b_2015.Lacy_Lab_7b_2015.main(Lacy_Lab_7b_2015.java:36)
Java Result: 1

来自编译器的

。

    public class Lacy_Lab_7b_2015 {

public static Scanner input = new Scanner(System.in);// scanner object to allow user input
public static int amount;// global variable defined by user to be used to have certain value of coins added so that they wll equal this value
public static int count = 0;
final public static int[] FACE_VALUES_OF_COINS = {100, 50, 25, 10, 5, 1};
public static int[] coinsUsed;

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    // TODO code application logic here
    amount = userAmount();
   // coinsUsed = coinsUsed(FACE_VALUES_OF_COINS,amount);

    for (int i = 0; i < FACE_VALUES_OF_COINS.length; i++) {
        int j = 0;
        if (FACE_VALUES_OF_COINS[i] < amount) {
            int count = amount / FACE_VALUES_OF_COINS[i];
           coinsUsed[j] = FACE_VALUES_OF_COINS[i];
            amount -= count * FACE_VALUES_OF_COINS[i];
        }//end if
    }//end for
    for (int i = 0; i < coinsUsed.length; i++) {
        System.out.println(coinsUsed[i]);
    }
}//end main

Answer 1

我建议你写一下

public static int [] coinsUsed;

作为

public static int [] coinsUsed = new int [5];