MyClass不能转换为java.lang.Comparable：java.lang.ClassCastException

本文介绍了MyClass不能转换为java.lang.Comparable：java.lang.ClassCastException的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我的项目中的类（简化）：

我正在做一个java项目，我遇到这个问题，不知道如何解决它。 p>

public class Item { private String itemID; 私人整数价格; public Integer getPrice（）{ return this.price; } } public class Store { private String storeID; private String address; } public class Stock { private Item item; 私人店铺; private整数itemCount; public Integer getInventoryValue（）{ return this.item.getPrice（）* this.itemCount; } }

然后我尝试排序一个 ArrayList 的股票，所以我创建另一个类叫$ code> CompareByValue

public class CompareByValue implements Comparator< Stock> { @Override public int compare（stock stock1，stock stock2）{ return（stock1.getInventoryValue（） - stock2.getInventoryValue（））; }

}

当我尝试运行程序时，会出现错误：

线程main中的异常java.lang.ClassCastException任何人都知道有什么问题？/ b>

=h2_lin>解决方案

这是因为库存不实现可比较的。实现它：

public class库存实现可比较&库存> { public int compareTo（Stock o）{ // ... } }

...或将 CompareByValue 的实例作为参数传递给 sort（） 方法：

Collections.sort（list，new CompareByValue（））;

I am doing a java project and I got this problem and don't know how to fix it.

The classes in my project (simplified):

public class Item { private String itemID; private Integer price; public Integer getPrice() { return this.price; } } public class Store { private String storeID; private String address; } public class Stock { private Item item; private Store store; private Integer itemCount; public Integer getInventoryValue() { return this.item.getPrice() * this.itemCount; } }

Then I try to sort an ArrayList of Stock so I create another class called CompareByValue

public class CompareByValue implements Comparator<Stock> { @Override public int compare(Stock stock1, Stock stock2) { return (stock1.getInventoryValue() - stock2.getInventoryValue()); }

}

When I try to run the program, it gives the error:

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

Anyone know what's wrong?

解决方案

It's because Stock isn't implementing Comparable. Either implement it:

public class Stock implements Comparable<Stock> { public int compareTo(Stock o) { // ... } }

... Or pass an instance of CompareByValue as parameter to the sort() method:

Collections.sort(list, new CompareByValue());