java - 为什么在调用以接口(interface)作为构造函数参数的类时出现 'source not found' 错误？

Question

我正在尝试使用接口(interface)创建一些字符串排序方法。应用程序驱动程序类调用主 SimplePriorityQueue 对象类，但它在进行此调用时传入实现该接口(interface)的类作为参数。有几个类实现该接口(interface)(一个按长度比较，一个按字母顺序(按值)比较，一个按反向长度等)，这就是为什么我被告知 SimplePriorityQueue 类中的一个构造函数应该能够处理所有这些。

使用 Eclipse 调试器时，只要 Application 类执行 pq = new SimplePriorityQueue(new StringByLength()); 行，就会弹出“找不到源”错误。如代码注释中所示。

这是我所拥有的:

<小时/>

//the Interface
package cs15200.review.srijitag;

public interface Comparator {
    public int compare(Object o1, Object o2);

}

<小时/>

这是排序类之一。还有好几个，不过几乎都是这样的

//StringByLength class, which sorts by length
package example.cs151xx;

import java.util.Comparator;


public class StringByLength implements Comparator {

  public int compare(Object o1, Object o2)
  {
    String s1 = (String)o1;
    String s2 = (String)o2;
    return s2.length() - s1.length();
  }

  public boolean equals(Object o)
  {return (o instanceof StringByLength);}
}

<小时/>

//the relevant portion of the Application class

import example.cs151xx.Prompt;
import cs15200.review.srijitag.SimplePriorityQueue;

import example.cs151xx.StringByLength;
import cs15200.review.srijitag.StringByLengthReverse;
import cs15200.review.srijitag.StringByValue;
import cs15200.review.srijitag.StringByValueIgnoreCase;
import cs15200.review.srijitag.IntegerIncreasing;

import java.util.Comparator;


public class Application {

  ////////////////
  //Driver Program
  ////////////////

    public static void main(String[] args)
    {
    //Construct object to test; let the user specify what Comparator
    //  object to construct to order the priority queue

      SimplePriorityQueue pq;
      char howPrioritize = Prompt.forChar("Enter how to prioritize queue\n  v (by value)\n  i (value ignore case)\n  l (by length)\n  r (by reverse length)\n\nChoice","virl");
      if (howPrioritize == 'v')
        pq = new SimplePriorityQueue(new StringByValue());
      else if (howPrioritize == 'i')
        pq = new SimplePriorityQueue(new StringByValueIgnoreCase());
      else if (howPrioritize == 'l')
        pq = new SimplePriorityQueue(new StringByLength()); //ERROR THROWN
      else
        pq = new SimplePriorityQueue(new StringByLengthReverse());

[...more code to finish up rest of driver class]

<小时/>

//The relevant parts SimplePriorityQueue class which has the constructors, accessors, and methods

package cs15200.review.srijitag;

import example.cs151xx.StringByLength;
import java.util.Comparator;

public class SimplePriorityQueue{
    public SimplePriorityQueue(Comparator whatever){
        check = whatever;
    }

    public void enqueue(Object item){

        if(list.length==rear+1)
            doubleSize();
        if (rear==-1)
            list[0]=item;
        else{
            for(int i=rear;i>=0;i--){
                int z = check.compare(item,list[i]);
                if(z<=0){
                    list[i+1]=list[i];
                    list[i]=item;                       }
                else{
                    list[i+1]=item;
                }
            }
        }
        rear++;
    }

[...more accessors and mutators]

          //instance variables
    private Object[] list=new Object[1];
    private int rear=-1;
    private Comparator check;


}

<小时/>

我知道这种基本格式(作为参数传递实现接口(interface)的对象，并使用该接口(interface)类型的对象作为参数)应该有效，因为我成功地尝试了以下简单示例:

package  cs15200.review.srijitag;
import example.cs151xx.StringByLength;
import java.util.Comparator;

public class temp {


    public static void main(String[] args) {
        Comparator z = new StringByLength();
        System.out.println( z.compare("hi", "what's up"));
        Comparator y = new StringByValue();
        System.out.println(y.compare("hi", "what's up"));

        System.out.println( lookee(new StringByLength())); //should return the same result as z.compare(...)
        System.out.println(lookee(new StringByValue())); //should return the same result as y.compare(...)
    }

    public static int lookee(Comparator test){
        return test.compare("hi", "what's up");

    }
}

<小时/>

那么我在 SimplePriorityQueue 类的构造函数中做错了什么？预先感谢您的帮助。

Answer 1

您实现了 java.util.Comparator 而不是 cs15200.review.srijitag.Comparator，其中未找到 java.util.Comparator 源当你调试时。