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| -rw-r--r-- | website/features/EqualsAndHashCode.html | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/website/features/EqualsAndHashCode.html b/website/features/EqualsAndHashCode.html index 0cad6b1b..b220e955 100644 --- a/website/features/EqualsAndHashCode.html +++ b/website/features/EqualsAndHashCode.html @@ -17,7 +17,8 @@ <p> Any class definition may be annotated with <code>@EqualsAndHashCode</code> to let lombok generate implementations of the <code>equals(Object other)</code> and <code>hashCode()</code> methods. By default, it'll use all non-static, non-transient fields, but you can exclude more fields by naming them in the optional <code>exclude</code> parameter to the annotation. Alternatively, you can specify exactly which fields you wish to be used by naming them in the <code>of</code> parameter. </p><p> - By setting <code>callSuper</code> to <em>true</em>, you can include the <code>equals</code> and <code>hashCode</code> methods of your superclass in the generated methods. For <code>hashCode</code>, the result of <code>super.hashCode()</code> is included in the hash algorithm, and for <code>equals</code>, the generated method will return false if the super implementation thinks it is not equal to the passed in object. Be aware that not all <code>equals</code> implementations handle this situation properly. However, lombok-generated <code>equals</code> implementations <strong>do</strong> handle this situation properly, so you can safely call your superclass equals if it, too, has a lombok-generated <code>equals</code> method.<br /> + If applying <code>@EqualsAndHashCode</code> to a class that extends another, this feature gets a bit trickier. Normally, auto-generating an <code>equals</code> and <code>hashCode</code> method for such classes is a bad idea, as the superclass also defines fields, which also need equals/hashCode code but + this code will not be generated. By setting <code>callSuper</code> to <em>true</em>, you can include the <code>equals</code> and <code>hashCode</code> methods of your superclass in the generated methods. For <code>hashCode</code>, the result of <code>super.hashCode()</code> is included in the hash algorithm, and for <code>equals</code>, the generated method will return false if the super implementation thinks it is not equal to the passed in object. Be aware that not all <code>equals</code> implementations handle this situation properly. However, lombok-generated <code>equals</code> implementations <strong>do</strong> handle this situation properly, so you can safely call your superclass equals if it, too, has a lombok-generated <code>equals</code> method. If you have an explicit superclass you are forced to supply some value for <code>callSuper</code> to acknowledge that you've considered it; failure to do so results in a warning.<br /> </p><p> Setting <code>callSuper</code> to <em>true</em> when you don't extend anything (you extend <code>java.lang.Object</code>) is a compile-time error, because it would turn the generated <code>equals()</code> and <code>hashCode()</code> implementations into having the same behaviour as simply inheriting these methods from <code>java.lang.Object</code>: only the same object will be equal to each other and will have the same hashCode. Not setting <code>callSuper</code> to <em>true</em> when you extend another class generates a warning, because unless the superclass has no (equality-important) fields, lombok cannot generate an implementation for you that takes into account the fields declared by your superclasses. You'll need to write your own implementations, or rely on the <code>callSuper</code> chaining facility. |