Question

在测试类中编译此for循环时遇到问题。

我目前在LabApp的测试课程中

import generics.StackFullException;
import generics.StackEmptyException;


public class Lab4App {
       public static void main(String[] args)throws StackFullException, StackEmptyException {
        try {
        DiscardPile<Card> discardPile = null; 
        discardPile = new DiscardPile<Card>();
        discardPile.push(new Card(8));
        discardPile.push(new Card(32));
        discardPile.push(new Card(48));
        discardPile.push(new Card(2));
        discardPile.push(new Card(17));
        discardPile.push(new Card(20)); //removeTopCard should remove all that's above
        discardPile.push(new Card(25));
        discardPile.push(new Card(50));
        discardPile.push(new Card(19));
        discardPile.push(new Card(41)); //10 Cards that must be popped

        for(int i = 0; i < discardPile.getSize(); i++) {
            Card var = discardPile.pop(); //pops the cards that are above
                System.out.println(var.getRankAsString() + " of " + var.getSuitAsString());
        }

        }
        catch (StackEmptyException SEE) {
            System.out.println("StackEmptyException: " + SEE.getMessage());
        }
        catch (StackFullException SFE) {
            System.out.println("StackFullException: " + SFE.getMessage());
       }
}
}

正在打印所需的输出

4 of Spades
8 of Diamonds
K of Spades
A of Diamonds
9 of Diamonds
6 of Diamonds
4 of Clubs
J of Spades
8 of Hearts
10 of Clubs

但返回

Exception in thread "main" java.util.EmptyStackException

结尾为红色

我认为问题是我创建的默认构造函数，该构造函数几乎与其中pop，peek和push是Stack类的Stack类相同

public class DiscardPile<T> extends Stack<T>  { //subclass of its parent Stack
    private T[] data;
    private int size;


    //private static final int maxSize = 52;

    public DiscardPile() throws StackFullException, StackEmptyException {
        //this.data = (T[]) new Object[maxSize];
        this.size = 52; //52 is supposed to be the max value
    }
    /**
     * Constructs a new Stack with capacity specified by user
     * @param size the size of the Stack
     */
    public DiscardPile(int size){
        //this.data = (T[]) new Object[size];
        this.size = 0;
    }

    public int getSize(){ // getter
        return this.size;
    }

如果我输入10而不是52，那么它可以正常工作，并且最后没有错误（因为有10张卡），如果我输入0，则它不会打印。零应该是初始值。

任何帮助将不胜感激！

编辑：公共类DiscardPile扩展了Stack实现Iterable {

//subclass of its parent Stack

    //private T[] data;
    private int size;


    private static final int MAX_SIZE = 52;

    public T push(T mink) {
        if (this.size() < this.MAX_SIZE) {
            super.push(mink);
        }
        return mink;
    }

    public DiscardPile() throws StackFullException, StackEmptyException {
        //this.data = (T[]) new Object[MAX_SIZE];
        this.size = 10; 
    }

    public DiscardPile(int size){
        //this.data = (T[]) new Object[size];
        this.size = 0;
    }

    public int getSize(){ // getter
        return this.size;
    }

Answer 1

您正在使用def make_greeting(name, greeting = "Hello"): return (greeting + " " + name + "!") # get name and greeting, send to make_greeting print(make_greeting(get_name(), get_greeting())) def get_name(): name_entry = input("enter a name: ") return name_entry def get_greeting(): greeting_entry = input("enter a greeting: ") return greeting_entry函数返回大小，但是大小始终被硬编码为getSize()，这将导致52循环尝试在没有可用空间时弹出更多内容

为什么您有一个实现for的自定义类？它似乎并没有增加太多功能。

如果您想继续使用自定义类，则可以：

使用一个for循环，当Stack<T>为false时会不断弹出。
使用默认情况下位于Stack类中的isEmpty()函数
在自定义类中编写一些内容，以在添加新项目时跟踪其大小。

Answer 2

您应该使用size()类提供的Stack函数，如果要强制执行最大限制，可以执行

public class DiscardPile<T> extends Stack<T> {

private static int MAX_SIZE = 52;

public T push(T mink) {
    if (this.size() < this.MAX_SIZE) {
        super.push(mink);
    }
    return mink;
}
}

Answer 3

每个人都指出了尺寸问题。您可以遍历自定义Stack类。实现可迭代的界面

public class DiscardPile<T> extends Stack<T> implements Iterable<T> {

   @Override
   public Iterator<T> iterator() {
     return new Iterator<T>() {
         // Implementation your iterator, methods like hasNext etc.
     }
   }
}

然后遍历堆栈

Iterator iterator = discardPile.iterator();
while (iterator.hasNext()) {
   //your code
}

问题与StackEmptyException异常

3 个答案: