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/**
* Copyright (c) 2014, University of Warsaw
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted
* provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this list of
* conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice, this list of
* conditions and the following disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package pl.edu.mimuw.cloudatlas.model;
/**
* Represents an attribute (without value, name only).
* <p>
* A valid attribute name is an identifier starting with a letter and containing only letters and digits. It can
* additionally start with an ampersand - such names are reserved for queries.
* <p>
* This class is immutable.
*/
public class Attribute {
private final String name;
/**
* Creates a new <code>Attribute</code> object with the specified <code>name</code>.
*
* @param name the name of the attribute
* @throws IllegalArgumentException if the <code>name</code> does not meet the rules
*/
public Attribute(String name) {
if(!name.matches("^&?[a-zA-Z]{1}[a-zA-z0-9_]*$"))
throw new IllegalArgumentException("Invalid name: may contain only letters, digits, underscores, "
+ "must start with a letter and may optionally have an ampersand at the beginning.");
this.name = name;
}
/**
* Indicates whether an <code>attribute</code> represents a query. This is true if and only if the attribute's name starts with an ampersand.
*
* @param attribute the attribute to check
* @return whether the <code>attribute</code> represents a query
*/
public static boolean isQuery(Attribute attribute) {
return attribute.getName().startsWith("&");
}
/**
* Gets the name of this attribute.
*
* @return string representing name
*/
public String getName() {
return name;
}
/**
* Returns a hash code value for this attribute. For proper behavior when using <code>Attribute</code> objects in
* <code>HashMap</code>, <code>HashSet</code> etc. this is the hash code of a string representing the attribute's name.
*
* @return hash code for this attribute
*/
@Override
public int hashCode() {
return name.hashCode();
}
/**
* Indicates whether another object is equal to this attribute.
*
* @param object the object to check
* @return true if and only if the <code>object</code> is an instance of <code>Attribute</code> class and has
* an identical name
*/
@Override
public boolean equals(Object object) {
if(object == null)
return false;
if(getClass() != object.getClass())
return false;
return name.equals(((Attribute)object).name);
}
/**
* Returns a textual representation of this attribute.
*
* @return the name of this attribute
*/
@Override
public String toString() {
return name;
}
}
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