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copied!<p>I like having as a template a "safer" equals() definition:</p> <pre><code> /** * Implement equals based on ${cursor}. <br /> * See {@link #compareTo(Object) compareTo} * @see java.lang.Object#equals(java.lang.Object) */ public boolean equals(final Object anObject) { boolean res = false; if(anObject == null) { return false; } if(anObject == this) { return true; } if(anObject.getClass() == this.getClass()) { res = this.compareTo(anObject) == 0; } return res; } </code></pre> <p>To be sure to always avoid <strong>Eq: equals method overrides equals in superclass and may not be symmetric</strong> (<code>EQ_OVERRIDING_EQUALS_NOT_SYMMETRIC</code>), where:</p> <blockquote> <p>This class defines an equals method that overrides an equals method in a superclass. Both equals methods methods use instanceof in the determination of whether two objects are equal. </p> <p>This is fraught with peril, since it is important that the equals method is symmetrical (in other words, <code>a.equals(b) == b.equals(a)</code>).<br> If <code>B</code> is a subtype of <code>A</code>, and <code>A</code>'s equals method checks that the argument is an <code>instanceof A</code>, and B's equals method checks that the argument is an <code>instanceof B</code>, it is quite likely that the equivalence relation defined by these methods is not symmetric.</p> </blockquote> <hr> <p>This is only for classes implementing <code>Comparable</code> and allows for:</p> <ul> <li>an implementation of equals which is always the same;</li> <li>all comparison logics to be located into one place only (the <code>compareTo()</code> function);</li> <li>the compliance with the javadoc of <code>Comparable#compareTo()</code> asking to ensure that <code>(x.compareTo(y)==0) == (x.equals(y))</code> (strongly recommended, but not strictly required though).</li> </ul>

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