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    <p>The commons/lang builders are great and I have been using them for years without noticeable performance overhead (with and without hibernate). But as Alain writes, the Guava way is even nicer:</p> <p>Here's a sample Bean:</p> <pre><code>public class Bean{ private String name; private int length; private List&lt;Bean&gt; children; } </code></pre> <p>Here's equals() and hashCode() implemented with Commons/Lang:</p> <pre><code>@Override public int hashCode(){ return new HashCodeBuilder() .append(name) .append(length) .append(children) .toHashCode(); } @Override public boolean equals(final Object obj){ if(obj instanceof Bean){ final Bean other = (Bean) obj; return new EqualsBuilder() .append(name, other.name) .append(length, other.length) .append(children, other.children) .isEquals(); } else{ return false; } } </code></pre> <p>and here with Java 7 or higher (inspired by Guava):</p> <pre><code>@Override public int hashCode(){ return Objects.hash(name, length, children); } @Override public boolean equals(final Object obj){ if(obj instanceof Bean){ final Bean other = (Bean) obj; return Objects.equals(name, other.name) &amp;&amp; length == other.length // special handling for primitives &amp;&amp; Objects.equals(children, other.children); } else{ return false; } } </code></pre> <p>Note: this code originally referenced Guava, but as comments have pointed out, this functionality has since been introduced in the JDK, so Guava is no longer required.</p> <p>As you can see the Guava / JDK version is shorter and avoids superfluous helper objects. In case of equals, it even allows for short-circuiting the evaluation if an earlier <code>Object.equals()</code> call returns false (to be fair: commons / lang has an <code>ObjectUtils.equals(obj1, obj2)</code> method with identical semantics which could be used instead of <code>EqualsBuilder</code> to allow short-circuiting as above).</p> <p>So: yes, the commons lang builders are very preferable over manually constructed <code>equals()</code> and <code>hashCode()</code> methods (or those awful monsters Eclipse will generate for you), but the Java 7+ / Guava versions are even better.</p> <p>And a note about Hibernate:</p> <p>be careful about using lazy collections in your equals(), hashCode() and toString() implementations. That will fail miserably if you don't have an open Session.</p> <hr> <p>Note (about equals()):</p> <p>a) in both versions of equals() above, you might want to use one or both of these shortcuts also:</p> <pre><code>@Override public boolean equals(final Object obj){ if(obj == this) return true; // test for reference equality if(obj == null) return false; // test for null // continue as above </code></pre> <p>b) depending on your interpretation of the equals() contract, you might also change the line(s)</p> <pre><code> if(obj instanceof Bean){ </code></pre> <p>to</p> <pre><code> // make sure you run a null check before this if(obj.getClass() == getClass()){ </code></pre> <p>If you use the second version, you probably also want to call <code>super(equals())</code> inside your <code>equals()</code> method. Opinions differ here, the topic is discussed in this question: </p> <blockquote> <p><a href="https://stackoverflow.com/q/8248970/342852">right way to incorporate superclass into a Guava Objects.hashcode() implementation?</a></p> </blockquote> <p>(although it's about <code>hashCode()</code>, the same applies to <code>equals()</code>)</p> <hr> <p><strong>Note (inspired by Comment from <a href="https://stackoverflow.com/users/274473/kayahr">kayahr</a>)</strong></p> <p><code>Objects.hashCode(..)</code> (just as the underlying <code>Arrays.hashCode(...)</code>) might perform badly if you have many primitive fields. In such cases, <code>EqualsBuilder</code> may actually be the better solution.</p>
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    1. POApache Commons equals/hashCode builder
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    1. USSean Patrick Floyd
    1. USSean Patrick Floyd
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    1. POApache Commons equals/hashCode builder
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    1. COThe same will be possible with Java 7 Objects.equals: http://download.oracle.com/javase/7/docs/api/java/util/Objects.html#equals%28java.lang.Object,%20java.lang.Object%29
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      1. USThomas Jung
    2. CO@Thomas nice, that's a step in the right direction!
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      1. USSean Patrick Floyd
    3. COI like the commons-lang features, but isn't it a bad practice to create a new object on each .hashCode() or .equals() call?
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