Question

I’m getting a ClassCastException in the below code, which doesn’t make much sense to me, as targetObject is a Comparable and current is a ToBeFound. Where are the Integer and String coming from?

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

As compareTo javadoc states:

ClassCastException – if the specified object’s type prevents it from being compared to this object.

It seems that your target is of a String type which is Comparable<String> and current.getValue() returns an object of Integer type.

You can try to do String.valueOf(current.getValue) if it works ok then I’m right. 🙂