Java：整数obj无法转换为Comparable [英] Java: Integer obj can't cast to Comparable

问题描述

在尝试从驱动程序类传递Integer对象作为我创建的SortedArray Generic类的函数的参数时遇到问题。从驱动程序类中，我将用户的int输入转换为要转换为我的SortedArray类的Comparable的Integer对象。

I'm having problems trying to pass an Integer object from a driver class as an argument for function of a SortedArray Generic class I created. From my driver class, I convert the user's int input into an Integer object to be cast onto Comparable of my SortedArray class.

我继续收到错误： Exception in线程主要 java.lang.ClassCastException：java.lang.Integer无法强制转换为Comparable。我看了看我同学的一些源代码，发现在设置参数/参数上没有什么区别，但他们的代码运行得很好。我一直在寻找试图找出自己犯了什么错误的小时，但仍然找不到为什么我的Integer对象无法转换为Comparable的原因。

I continue to receive the error: "Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to Comparable". I took a look at some of my classmates' source codes only to find little difference in setting the arguments/parameters yet they have their code working just fine. I've been looking for hours trying to find what error I've made and I still can't find why my Integer object can't be cast to Comparable.

这是我的SortedArray类别中的一些内容

Here's a bit from my SortedArray Class

public class SortedArray implements Comparable{
    public int size;
public int increment;
public int top;
    Comparable[] a = new Comparable [size];

public SortedArray(int initialSize, int incrementAmount)
{
        top = -1;
        size = initialSize;
        increment = incrementAmount;

}
public int appropriatePosition(Comparable value)
{
        int hold = 0;
        if(top == -1)
        {
            return 0;
        }
        else
        {    
            for(int i = 0; i <= top; i++)
            {
                if(a[i].compareTo(value) > 0)
                {
                    hold = i;
                    break;
                }
            }
        }
        return hold;
}

public void insert(Comparable value) //The function that my driver class needs to access
{
        //Shifting numbers to the top
        if(full() == true)
        {
            Comparable[] tempArray = new Comparable[top + increment];
            for(int i= 0; i< size; i++)
            {
                tempArray[i]= a[i];
                a  = tempArray;
            }
            size = top + increment;
        }
        if(a[appropriatePosition(value) + 1] != null)
        {
            for(int i = top; i < appropriatePosition(value); i--)
            {
                a[i + 1] = a[i];
            }
        }
        a[appropriatePosition(value) + 1]= value;
    }

这是我的驱动程序类的代码，该类传递Integer Object insertObj作为参数SortedArray的插入函数。

Here's the code for my driver class that passes Integer Object insertObj as an argument for SortedArray's insert function.

public class IntDriver  {
 public static void main(String[] args)
 {
     Scanner keyboard = new Scanner(System.in);
     //Creating variables
     int data;
     boolean check = false;
     int choice;
     int size = 5;
     int increment = 3;
     SortedArray b = new SortedArray(size, increment);
     //Creating Menu
     while(check == false)
     {
     System.out.println("Please choose through options 1-6.");
     System.out.println("1. Insert\n2. Delete\n3. Clear\n4. Smallest\n5. Largest\n6. Exit");
     choice = keyboard.nextInt();
     switch(choice)
         {
         case 1:
             System.out.println("Type the int data to store in array location.");
             data = keyboard.nextInt();
             Integer insertObj = new Integer(data);
             b.insert(insertObj);// Here's where I lay "insertObj" as an argument for the SortedArray function.
             System.out.println("The value " + data + " is inserted");
            break;

推荐答案

问题是 Integer 扩展了 java.lang.Comparable ，那么您的 Comparable 不是 java.lang.Comparable 。查看错误消息，您的 Comparable 来自默认软件包，而不是 java.lang ：

The problem is that Integer extends java.lang.Comparable, then your Comparable is not a java.lang.Comparable. Look at the error message, your Comparable comes from the default package rather than java.lang:

Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to Comparable

也就是说，您不能将 java.lang.Integer 转换为自己的类

That is, you can't cast java.lang.Integer to your own class

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