java - Java 中的 ClassCastException

Question

我在下面的代码中遇到了 ClassCastException，这对我来说没有多大意义，因为 targetObject 是一个 Comparable，而 current 是一个 ToBeFound。整数和字符串从哪里来？

ToBeFound origin = new ToBeFound();
public ToBeFound findWrapper(Comparable targetObject)
{
    return find(origin, targetObject);
}

private ToBeFound find(ToBeFound current, Comparable targetObject)
{
    if (current == null)
        {
        return null;
        }

    System.out.println(targetObject.compareTo(current.getValue()));
     // Exception in thread "main" java.lang.ClassCastException: 
     // java.lang.Integer cannot be cast to java.lang.String

    return new ToBeFound();
}

//body of main() that calls the methods
master.find( (Comparable) scanner.next()); 
   // Scanner is a java.util.Scanner scanning System.in

Answer 1

如compareTo javadoc 指出:

ClassCastException - if the specified object's type prevents it from being compared to this object.

看来你的target是 String类型为Comparable<String>和current.getValue()返回 Integer 的对象类型。

你可以尝试做String.valueOf(current.getValue)如果它工作正常那么我是对的。 :)