Question

我已经获得了这个数组，可以在一个类中用于作业。

/**
 * compactHand - THIS METHOD IS SUPPLIED FOR YOU!
 * re-order the array so that all cards occupy the early indices, i.e. 0,1,2,...
 * and that all the nulls are in the higher indices. 
 * Also count the number of cards in the array and set ncard accordingly.
 * Example: if array is [Kclub][null][2diamond][null][7spade]
 * then this routine sets array to [Kclub][2diamond][7spade][null][null] and sets ncard to 3.
 * Note that the relative order of cards is not changed.
 */
private void compactHand(){
    int nc=0, ix=0, nullix=-1;
    // find first null
    do{
        if (cards[ix]==null){
            nullix = ix;
            break;
        }
    } while (++ix<cards.length);
    if (nullix==-1){
        // there were no nulls.  set ncards and return.
        ncard = cards.length;
        return;
    }
    nc = nullix;
    // loop to end of array and swap cards for nulls
    for(ix=nullix; ix<cards.length; ix++)
        if (!(cards[ix]==null)){
            cards[nullix++] = cards[ix];
            cards[ix] = null;
            nc++;
        }
    ncard = nc; 
}

我已经完成了大部分任务，但是对于其中一种方法，我需要在名为cards的数组中调用它。我尝试使用以下方式调用它：

cards.compactHand();

该方法不接受数组作为参数，但在我需要完成的方法中，指令明确指出要使用它。

/**
 * delete Cards at specified indices and compact the array.
 * if any indices do not correspond to cards then the array must be unchanged
 *   and this member returns false.
 * otherwise the specified cards are deleted, the array compacted and true returned.
 * @param index index of array element to delete
 * @return true if all elements successfully deleted, false if none deleted.
 */

该方法被标记为私有，但我可以访问它，因为它在同一个类中。

对此有任何帮助将不胜感激。

Answer 1

cards数组应该是类中的实例变量。实例变量在类的方法之外声明，通常在它的开头。然后可以从该类的任何方法调用它们。 This answer有一些关于实例变量的例子。

Answer 2

应该有另一个方法返回一个可以调用方法compactHand();的数组，否则这个方法不返回数组。我已经声明了一些数组是一个构造函数，这可能有帮助

public class Test {

    private String[] cards;
    private int ncard;

    public Test(String[] cards) {
        this.cards = new String[cards.length];
        for(int i = 0; i <cards.length; i++){
            this.cards[i] = cards[i];
        } 

    }

    private void compactHand() {
        int nc = 0, ix = 0, nullix = -1;
        // find first null
        do {
            if (cards[ix] == null) {
                nullix = ix;
                break;
            }
        } while (++ix < cards.length);
        if (nullix == -1) {
            // there were no nulls.  set ncards and return.
            ncard = cards.length;
            return;
        }
        nc = nullix;
        // loop to end of array and swap cards for nulls
        for (ix = nullix; ix < cards.length; ix++)
            if (!(cards[ix] == null)) {
                cards[nullix++] = cards[ix];
                cards[ix] = null;
                nc++;
            }
        ncard = nc;
    }

    public static void main(String[] args) {
        String[] cards = {"1", "2", "king", "ace"};
        Test test = new Test(cards);
        test.compactHand();
        for (int i = 0; i < cards.length; i++) {
            System.out.println(Arrays.toString(cards));
        }

    }

}

如何用数组调用此方法？有可能吗？

2 个答案: