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<h1>Converting Method Arguments - General Rules</h1>
<p>Having decided which method to call, Saxon has to convert the supplied XPath argument values to the
Java objects required by this method.</p>
<p>If the expected type is <code>Object</code>, the supplied value must either be a singleton, or an empty sequence.
If it is an empty sequence, null will be passed. If it is a singleton node, an instance of <a class="bodylink" href="../../javadoc/net/sf/saxon/om/NodeInfo.html"><code>net.sf.saxon.om.NodeInfo</code></a>
will be passed. If it is a wrapped Java object, that Java object will be passed.
If it is a singleton atomic value, the value will be converted to the nearest equivalent Java object: for example
an <code>xs:boolean</code> becomes <code>java.lang.Boolean</code>, an <code>xs:string</code> becomes <code>java.lang.String</code>,
and so on. An untyped atomic value is treated as a string. An <code>xs:integer</code> (even if it belongs to a subtype such as
<code>xs:short</code>) is converted to a Java <code>BigInteger</code>. The more specialized XML Schema primitive types such as
<code>xs:hexBinary</code> and <code>xs:duration</code> are passed in their native Saxon representation (a subclass of
<a class="bodylink" href="../../javadoc/net/sf/saxon/value/AtomicValue.html"><code>net.sf.saxon.value.AtomicValue</code></a>).</p>
<p>If the expected type is one of the Saxon-specific classes (<a class="bodylink" href="../../javadoc/net/sf/saxon/om/SequenceIterator.html"><code>SequenceIterator</code></a>,
<a class="bodylink" href="../../javadoc/net/sf/saxon/om/ValueRepresentation.html"><code>ValueRepresentation</code></a>,
<a class="bodylink" href="../../javadoc/net/sf/saxon/om/Item.html"><code>Item</code></a>,
<a class="bodylink" href="../../javadoc/net/sf/saxon/value/Value.html"><code>Value</code></a>,
<a class="bodylink" href="../../javadoc/net/sf/saxon/value/AtomicValue.html"><code>AtomicValue</code></a>,
<a class="bodylink" href="../../javadoc/net/sf/saxon/value/SequenceExtent.html"><code>SequenceExtent</code></a>), then the value is passed unchanged. An error occurs if the supplied value contains
more than one item and the expected type does not allow this.</p>
<p>If the expected type implements <code>java.util.Collection</code>, Saxon attempts to convert each value in the supplied sequence
to the most appropriate Java class, following the same rules as when converting a singleton to <code>java.lang.Object</code>.
This process takes no account of parameterized collection types (such as <code>List<String></code>). If the required
collection type accepts an <code>java.util.ArrayList</code>, Saxon will create an <code>ArrayList</code> to hold the values; otherwise
it will attempt to instantiate the required type of collection, which will only work if it is a concrete class with a zero-argument
public constructor (so it will fail, for example, if the required type is <code>java.util.Set</code>). If an empty sequence is
supplied as the argument value, this is converted to an empty Collection.</p>
<p>If the required type is an array, Saxon will attempt to create an array of the required type. This will not always succeed,
for example if the array has type <code>X[]</code> where X is an interface rather than a concrete class. If it is an array of items
or nodes, the nodes in the supplied sequence will be inserted into the array directly; if it is an array of a type such as integer or
double, the sequence will first be atomized.</p>
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