/*
* Copyright 2012 Daniel Bechler
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package de.danielbechler.diff.selector;
/**
* Serves mainly as marker class and enforces the proper implementation of hashCode(), equals() and toString()
* for all element selectors.
*
* @author Daniel Bechler
*/
public abstract class ElementSelector
{
public abstract String toHumanReadableString();
/**
* Must be implemented in a way so that this element can be distinguished from the other ones.
*
* @param obj The object to check equality against.
* @return <code>true</code> is the given object equals this one, otherwise <code>false</code>.
*/
public abstract boolean equals(Object obj);
/**
* Make sure to implement this properly. If two elements are equal, their hash code must be equal as well.
* However, it is absolutely okay if two unequal elements return the same hash code. A simple implementation
* could just return <code>0</code>.
*
* @return The hash code of this element.
*/
public abstract int hashCode();
/**
* The string representation will only be used to print readable property paths for debug purposes.
*
* @return A string representation of this element for debug purposes.
*/
public final String toString()
{
return toHumanReadableString();
}
}