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java - 我不断收到 [Ljava.lang.Object;无法转换为 [Ljava.lang.Comparable 错误

转载 作者:太空宇宙 更新时间:2023-11-04 14:05:40 29 4
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我正在创建一个实现 GenericList 类的 ListType 类。 findMax、findMin 和 printAll 方法是我添加到 ListType 中的。我相信问题出在我扩展的 Comparable 和 list=(E[])(new Object[cap]) 之间。

import java.util.*;
import java.io.*;

public class ListType<E extends Comparable<E>> implements GeneralList<E>
{

private final int default_cap = 10;
private final int resize_fac = 2;
private E[] list;
private int numElements;


public ListType()
{
list = (E[])(new Object[default_cap]);
numElements = 0;
}

public ListType(int cap)
{
if (cap < 1)
throw new IllegalArgumentException();

list = (E[])(new Object[cap]);
numElements = 0;
}


public void add(E element)
{
if (numElements == list.length)
resize();

list[numElements] = element;

numElements++;
}

public void add(int index, E element)
{

if (index > numElements || index < 0)
throw new IndexOutOfBoundsException();

if (numElements == list.length)
resize();

for (int i = numElements; i > index; i--)
list[i] = list[i - 1];

list[index] = element;

numElements++;
}

public void clear()
{
for (int i = 0; i<list.length; i++)
list[i] = null;
numElements = 0;
}

public boolean contains(E element)
{
int index = 0;
boolean found = false;

while (!found && index < numElements)
{
if (list[index].equals(element))
found = true;
index++;
}

return found;
}


public E get(int index)
{
if (index >= numElements || index < 0)
throw new IndexOutOfBoundsException();
return list[index];
}

public int indexOf(E element)
{
int index = 0;
boolean found = false;

while (!found && index < numElements)
{
if (list[index].equals(element))
found = true;
else
index++;
}


if (!found)
index = -1;
return index;
}

public boolean isEmpty()
{
return (numElements == 0);
}


public boolean remove(E element)
{
int index = 0;
boolean found = false;

while (!found && index < numElements)
{
if (list[index].equals(element))
{
list[index] = null;
found = true;
}
index++;
}


if (found)
{
while(index < numElements)
{
list[index - 1] = list[index];
index++;
}

numElements--;
}

return found;
}

public E remove(int index)
{
if (index >= numElements || index < 0)
throw new IndexOutOfBoundsException();

E temp = list[index];
list[index] = null;
index++;

while(index < numElements)
{
list[index - 1] = list[index];
index++;
}

numElements--;

return temp;
}

private void resize()
{
int newLength = list.length * resize_fac;

E[] tempList = (E[])(new Object[newLength]);

for (int index = 0; index < numElements; index++)
tempList[index] = list[index];

list = tempList;
}

public E set(int index, E element)
{
if (index >= numElements || index < 0)
throw new IndexOutOfBoundsException();

E temp = list[index];

list[index] = element;

return temp;
}

public int size()
{
return numElements;
}


public String[] toStringArray()
{
String[] strArray = new String[numElements];

for (int index = 0; index < numElements; index++)
strArray[index] = list[index].toString();


return strArray;
}

//This method will find the minimum element using the Comparable implemented
public E findMin()
{
E min = list[0];
for(int i=1; i<list.length; i++)
{
if(min.compareTo(list[i]) > 0)
min = list[i];
}

return min;
}

//This method will find the maximium element using the Comparable implemented
public E findMax()
{
E max = list[0];
for(int i=1; i<list.length; i++)
{
if(max.compareTo(list[i]) < 0)
max = list[i];
}
return max;
}


//This method print all the elements in the list simply using the for.
public void printAll()
{
for(int i=0; i<list.length; i++)
System.out.print(list[i] + " ");
}

//This is the main class which executes the program
public static void main(String[] args) throws IOException{

//This will read the elements from the file.
File file = new File("document.txt");
Scanner inputFile = new Scanner(file);
String line1 = inputFile.nextLine();
String[] arrayLine = line1.split(" ");

//This will create the list of the class above.
ListType<Double> numbers = new ListType<Double>();

for(int i=0; i<numbers.size(); i++){
numbers.add(Double.parseDouble(arrayLine[i]));
}

System.out.println("The following elements in the file are: ");
numbers.printAll();
System.out.println(" ");

System.out.println("The minimium element in the file is " + numbers.findMin());
System.out.println(" ");
System.out.println("The maximium element in the file is " + numbers.findMax());



}

}

最佳答案

private E[] list; 更改为 private Object[] list; 并删除构造函数中的 (E[]) 转换。

无论您在 get 方法中使用 list[index],您都需要显式转换实例,如 (E)list[index]

关于java - 我不断收到 [Ljava.lang.Object;无法转换为 [Ljava.lang.Comparable 错误,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28892318/

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