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Groovy supports operator overloading which makes working with Numbers, Collections, Maps and various other data structures easier to use.

Various operators in Groovy are mapped onto regular Java method calls on objects. 
This allows you the developer to provide your own Java or Groovy objects which can take advantage of operator overloading. The following table describes the operators supported in Groovy and the methods they map to.
<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"> Operator </th>
<th class="confluenceTh"> Method </th>
</tr>
<tr>
<td class="confluenceTd"> a + b </td>
<td class="confluenceTd"> a.plus(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a - b </td>
<td class="confluenceTd"> a.minus(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a * b </td>
<td class="confluenceTd"> a.multiply(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a ** b </td>
<td class="confluenceTd"> a.power(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a / b </td>
<td class="confluenceTd"> a.div(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a % b </td>
<td class="confluenceTd"> a.mod(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a | b </td>
<td class="confluenceTd"> a.or(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a &amp; b </td>
<td class="confluenceTd"> a.and(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a ^ b </td>
<td class="confluenceTd"> a.xor(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a++ or ++a </td>
<td class="confluenceTd"> a.next() </td>
</tr>
<tr>
<td class="confluenceTd"> a-- or --a </td>
<td class="confluenceTd"> a.previous() </td>
</tr>
<tr>
<td class="confluenceTd"> a[b] </td>
<td class="confluenceTd"> a.getAt(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a[b] = c </td>
<td class="confluenceTd"> a.putAt(b, c) </td>
</tr>
<tr>
<td class="confluenceTd"> a &lt;&lt; b </td>
<td class="confluenceTd"> a.leftShift(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a &gt;&gt; b </td>
<td class="confluenceTd"> a.rightShift(b) </td>
</tr>
<tr>
<td class="confluenceTd"> switch(a) { case(b) : } </td>
<td class="confluenceTd"> b.isCase(a) </td>
</tr>
<tr>
<td class="confluenceTd"> ~a </td>
<td class="confluenceTd"> a.bitwiseNegate() </td>
</tr>
<tr>
<td class="confluenceTd"> -a </td>
<td class="confluenceTd"> a.negative() </td>
</tr>
<tr>
<td class="confluenceTd"> +a </td>
<td class="confluenceTd"> a.positive() </td>
</tr>
</tbody></table>

Note that all the following comparison operators handle nulls gracefully avoiding the throwing of <a href="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/NullPointerException.html">java.lang.NullPointerException</a>
<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"> Operator </th>
<th class="confluenceTh"> Method </th>
</tr>
<tr>
<td class="confluenceTd"> a == b </td>
<td class="confluenceTd"> a.equals(b) or a.compareTo(b) == 0 ** </td>
</tr>
<tr>
<td class="confluenceTd"> a != b </td>
<td class="confluenceTd"> ! a.equals(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a &lt;=&gt; b </td>
<td class="confluenceTd"> a.compareTo(b) </td>
</tr>
<tr>
<td class="confluenceTd"> a &gt; b </td>
<td class="confluenceTd"> a.compareTo(b) &gt; 0 </td>
</tr>
<tr>
<td class="confluenceTd"> a &gt;= b </td>
<td class="confluenceTd"> a.compareTo(b) &gt;= 0 </td>
</tr>
<tr>
<td class="confluenceTd"> a &lt; b </td>
<td class="confluenceTd"> a.compareTo(b) &lt; 0 </td>
</tr>
<tr>
<td class="confluenceTd"> a &lt;= b </td>
<td class="confluenceTd"> a.compareTo(b) &lt;= 0 </td>
</tr>
</tbody></table>

** Note: The == operator doesn't always exactly match the .equals() method. You can think of them as equivalent in most situations. In situations where two objects might be thought &quot;equal&quot; via normal Groovy &quot;coercion&quot; mechanisms, the == operator will report them as equal; the .equals() method will not do so if doing so would break the normal rules Java has around the equals method. Expect further improvements to Groovy over time to provide clearer, more powerful and more consistent behavior in this area.

<h2>Notes about operations</h2>

Also in Groovy comparison operators handle nulls gracefully. So that a == b will never throw a NullPointerException whether a or b or both are null.
<table class="wysiwyg-macro" data-macro-name="code" data-macro-default-parameter="java" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6amF2YX0&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 a = null
def b = "foo"

assert a != b
assert b != a
assert a == null
</pre></td></tr></table>
In addition when comparing numbers of different types the type coercion rules apply to convert numbers to the largest numeric type before the comparison. So the following is valid in Groovy
<table class="wysiwyg-macro" data-macro-name="code" data-macro-default-parameter="java" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6amF2YX0&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
Byte a = 12
Double b = 10

assert a instanceof Byte
assert b instanceof Double

assert a > b
</pre></td></tr></table>