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<h2>Operators</h2><p>In general all operators <a href="http://java.sun.com/docs/books/tutorial/java/nutsandbolts/operators.html">supported in Java</a> are identical in Groovy. Groovy goes a step further by allowing you to <a class="confluence-link" href="/display/GROOVY/Operator+Overloading" data-linked-resource-id="2764" data-linked-resource-type="page" data-linked-resource-default-alias="Operator Overloading" data-base-url="http://docs.codehaus.org">customize behavior</a> of operators on Groovy types.</p><p><img class="editor-inline-macro" src="/plugins/servlet/confluence/placeholder/macro?definition=e3RvYzptYXhMZXZlbD04fG1pbkxldmVsPTN9&amp;locale=en_GB&amp;version=2" data-macro-name="toc" data-macro-parameters="maxLevel=8|minLevel=3"></p><h3>Arithmetic and Conditional Operators</h3><p>See <a class="confluence-link" href="/display/GROOVY/Operator+Overloading" data-linked-resource-id="2764" data-linked-resource-type="page" data-linked-resource-default-alias="Operator Overloading" data-base-url="http://docs.codehaus.org">Operator Overloading</a> for a list of the common operators that Groovy supports.</p><p>In addition, Groovy supports the ! (not) operator as follows:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>def expression = false
assert !expression
</pre></td></tr></table><p>For more details about how expressions are corced to a boolean value, see: <a class="confluence-link" href="/display/GROOVY/Groovy+Truth" data-linked-resource-id="31358992" data-linked-resource-type="page" data-linked-resource-default-alias="Groovy Truth" data-base-url="http://docs.codehaus.org">Groovy Truth</a>.</p><h3>Collection-based Operators</h3><h4>Spread Operator (*.)</h4><p>The Spread Operator is used to invoke an action on all items of an aggregate object. It is equivalent to calling the collect method like so:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>parent*.action                             //equivalent to:
parent.collect{ child -> child?.action }
</pre></td></tr></table><p>The action may either be a method call or property access, and returns a list of the items returned from each child call. As an example:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>assert ['cat', 'elephant']*.size() == [3, 8]
</pre></td></tr></table><p>The Spread operator will work as expected with most of the aggregate-like classes within Groovy. You can also customize your own classes to use it by defining your own <code>iterator()</code> method as this example shows:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>class Person { String name }
class Twin {
  Person one, two
  def iterator() {
    return [one, two].iterator()
  }
}

def tw = new Twin(one: new Person(name:'Tom'),
                  two: new Person(name:'Tim'))
assert tw*.name == ['Tom', 'Tim']
// expanded equivalent of above:
assert tw.collect{ it.name } == ['Tom', 'Tim']
</pre></td></tr></table><h3>Object-Related Operators</h3><ul><li><a class="confluence-link" href="/display/GROOVY/Using+invokeMethod+and+getProperty" data-linked-resource-id="9765915" data-linked-resource-type="page" data-linked-resource-default-alias="Using invokeMethod and getProperty" data-base-url="http://docs.codehaus.org">invokeMethod and get/setProperty </a> (.)</li><li>Java field (.@)</li><li>The spread java field (*.@)</li><li>Method Reference (.&amp;)</li><li>'as' - &quot;manual coercion&quot; - <code>asType(t)</code> method</li><li>Groovy == ( <code>equals()</code>) behavior.<ul><li>&quot;is&quot; for identity</li></ul></li><li>The <em>instanceof</em> operator (as in Java)</li></ul><h5>Java field (.@)</h5><p>Groovy dynamically creates getter method for all your fields that can be referenced as properties:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>class X
{
    def field
}

x = new X()
x.field = 1
println x.field    // 1
</pre></td></tr></table><p>You can override these getters with your own implementations if you like:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>class X
{
    def field

def getField()
    {
        field += 1
    }
}

x = new X()
x.field = 1
println x.field   // 2
</pre></td></tr></table><p>The @ operator allows you to override this behavior and access the field directly, so to extend the previous sample:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>println x.@field   // 1
</pre></td></tr></table><p>It should be mentioned that, while interesting, this is probably not a good thing to do unless you really need to. Overriding a public interface to access the internal state of an object probably means you are about to break something. Not even recommended for use in tests since it increases coupling unnecessarily.</p><h3>Other Operators</h3><ul><li><p><code>getAt(index)</code> and <code>putAt(index, value)</code> for the subscript operator (e.g. foo[1] or foo['bar'], i.e. index is either an int or String)</p></li><li>Range Operator (..) - see <a class="confluence-link" href="/display/GROOVY/Collections#Collections-Collections-Ranges" data-anchor="Collections-Ranges" data-linked-resource-id="2732" data-linked-resource-type="page" data-linked-resource-default-alias="Collections#Collections-Ranges" data-base-url="http://docs.codehaus.org">Collections#Collections-Ranges</a></li><li><code>isCase()</code> for the membership operator (in)</li></ul><h4>Elvis Operator (?: )</h4><p>The &quot;Elvis operator&quot; is a shortening of Java's <a href="http://java.sun.com/docs/books/tutorial/java/nutsandbolts/op2.html">ternary operator</a>. One instance of where this is handy is for returning a 'sensible default' value if an expression resolves to <code>false</code> or <code>null</code>. A simple example might look like this:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>def displayName = user.name ? user.name : "Anonymous" //traditional ternary operator usage

def displayName = user.name ?: "Anonymous"  // more compact Elvis operator - does same as above</pre></td></tr></table><h4>Safe Navigation Operator (?.)</h4><p>The Safe Navigation operator is used to avoid a NullPointerException. Typically when you have a reference to an object you might need to verify that it is not null before accessing methods or properties of the object. To avoid this, the safe navigation operator will simply return <code>null</code> instead of throwing an exception, like so:</p><table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>def user = User.find( "admin" )           //this might be null if 'admin' does not exist
def streetName = user?.address?.street    //streetName will be null if user or user.address is null - no NPE thrown
</pre></td></tr></table><h3>Regular Expression Operators</h3><ul><li>find (=~)</li><li>match (==~)</li></ul><p>For more details, see: <a class="confluence-link" href="/display/GROOVY/Regular+Expressions" data-linked-resource-id="2768" data-linked-resource-type="page" data-linked-resource-default-alias="Regular Expressions" data-base-url="http://docs.codehaus.org">Regular Expressions</a></p><h3>Table of Operators</h3><table class="confluenceTable"><tbody><tr><th class="confluenceTh"><p>Operator Name</p></th><th class="confluenceTh"><p>Symbol</p></th><th class="confluenceTh"><p>Description</p></th></tr><tr><td class="confluenceTd"><p>Spaceship</p></td><td class="confluenceTd"><p>&lt;=&gt;</p></td><td class="confluenceTd"><p>Useful in comparisons, returns -1 if left is smaller 0 if == to right or 1 if greater than the right</p></td></tr><tr><td class="confluenceTd"><p>Regex find</p></td><td class="confluenceTd"><p>=~</p></td><td class="confluenceTd"><p>Find with a regular expresion? See <a class="confluence-link" href="/display/GROOVY/Regular+Expressions" data-linked-resource-id="2768" data-linked-resource-type="page" data-linked-resource-default-alias="Regular Expressions" data-base-url="http://docs.codehaus.org">Regular Expressions</a></p></td></tr><tr><td class="confluenceTd"><p>Regex match</p></td><td class="confluenceTd"><p>==~</p></td><td class="confluenceTd"><p>Get a match via a regex? See <a class="confluence-link" href="/display/BOO/Regular+Expressions" data-linked-resource-id="17614" data-linked-resource-type="page" data-linked-resource-default-alias="Regular Expressions" data-base-url="http://docs.codehaus.org">Regular Expressions</a></p></td></tr><tr><td class="confluenceTd"><p><a href="http://docs.codehaus.org/display/GROOVY/Operators#Operators-Javafield%28.@%29">Java Field Override </a></p></td><td class="confluenceTd"><p>.@</p></td><td class="confluenceTd"><p>Can be used to override generated properties to provide access to a field</p></td></tr><tr><td class="confluenceTd"><p><a href="http://docs.codehaus.org/display/GROOVY/Operators#Operators-SpreadOperator%28.%29">Spread</a></p></td><td class="confluenceTd"><p>*.</p></td><td class="confluenceTd"><p>Used to invoke an action on all items of an aggregate object</p></td></tr><tr><td class="confluenceTd"><p>Spread Java Field</p></td><td class="confluenceTd"><p>*.@</p></td><td class="confluenceTd"><p>Amalgamation of the above two</p></td></tr><tr><td class="confluenceTd"><p>Method Reference</p></td><td class="confluenceTd"><p>.&amp;</p></td><td class="confluenceTd"><p>Get a reference to a method, can be useful for creating closures from methods</p></td></tr><tr><td class="confluenceTd"><p>asType Operator</p></td><td class="confluenceTd"><p>as</p></td><td class="confluenceTd"><p>Used for groovy casting, coercing one type to another.</p></td></tr><tr><td class="confluenceTd"><p>Membership Operator</p></td><td class="confluenceTd"><p>in</p></td><td class="confluenceTd"><p>Can be used as replacement for collection.contains()</p></td></tr><tr><td class="confluenceTd"><p>Identity Operator</p></td><td class="confluenceTd"><p>is</p></td><td class="confluenceTd"><p>Identity check. Since == is overridden in Groovy with the meaning of equality we need some fallback to check for object identity.</p></td></tr><tr><td class="confluenceTd"><p><a href="http://docs.codehaus.org/display/GROOVY/Operators#Operators-SafeNavigationOperator%28%3F.%29">Safe Navigation</a></p></td><td class="confluenceTd"><p>?.</p></td><td class="confluenceTd"><p>returns nulls instead of throwing NullPointerExceptions</p></td></tr><tr><td class="confluenceTd"><p><a href="http://docs.codehaus.org/display/GROOVY/Operators#Operators-ElvisOperator%28%3F%3A%29">Elvis Operator</a></p></td><td class="confluenceTd"><p>?:</p></td><td class="confluenceTd"><p>Shorter ternary operator</p></td></tr></tbody></table>