src/java/org/apache/commons/lang/IllegalClassException.java

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package org.apache.commons.lang;

/**
 * <p>Thrown when an object is an instance of an unexpected type (a class or interface).</p>
 * 
 * @author Matthew Hawthorne
 * @author Gary Gregory
 * @since 2.0
 * @version $Id: IllegalClassException.java,v 1.4 2003/07/14 22:25:02 bayard Exp $
 */
public class IllegalClassException extends IllegalArgumentException {

    /**
     * <p>Instantiates with the specified types (classes or interfaces).</p>
     * 
     * @param expected  the expected type
     * @param actual  the actual type
     */
    public IllegalClassException(Class expected, Class actual) {
        super(
            "Expected: "
                + safeGetClassName(expected)
                + ", actual: "
                + safeGetClassName(actual));
    }

    /**
     * <p>Instantiates with the specified message.</p>
     * 
     * @param message  the exception message
     */
    public IllegalClassException(String message) {
        super(message);
    }

    /**
     * <p>Returns the class name or <code>null</code> if the class is
     * <code>null</code>.</p>
     * 
     * @param cls  a <code>Class</code>
     * @return the name of <code>cls</code>, or <code>null</code> if if <code>cls</code> is <code>null</code>.
     */
    private static final String safeGetClassName(Class cls) {
        return cls == null ? null : cls.getName();
    }

}