MagicNumberFileFilter.html

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MagicNumberFileFilter (Commons IO 1.5-SNAPSHOT)
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org.apache.commons.io.filefilter</FONT>
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Class MagicNumberFileFilter</H2>
<PRE>
<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">java.lang.Object</A>
  <IMG SRC="../../../../../resources/inherit.gif" ALT="extended by "><A HREF="../../../../../org/apache/commons/io/filefilter/AbstractFileFilter.html" title="class in org.apache.commons.io.filefilter">org.apache.commons.io.filefilter.AbstractFileFilter</A>
      <IMG SRC="../../../../../resources/inherit.gif" ALT="extended by "><B>org.apache.commons.io.filefilter.MagicNumberFileFilter</B>
</PRE>
<DL>
<DT><B>All Implemented Interfaces:</B> <DD><A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/FileFilter.html?is-external=true" title="class or interface in java.io">FileFilter</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/FilenameFilter.html?is-external=true" title="class or interface in java.io">FilenameFilter</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/Serializable.html?is-external=true" title="class or interface in java.io">Serializable</A>, <A HREF="../../../../../org/apache/commons/io/filefilter/IOFileFilter.html" title="interface in org.apache.commons.io.filefilter">IOFileFilter</A></DD>
</DL>
<HR>
<DL>
<DT><PRE>public class <B>MagicNumberFileFilter</B><DT>extends <A HREF="../../../../../org/apache/commons/io/filefilter/AbstractFileFilter.html" title="class in org.apache.commons.io.filefilter">AbstractFileFilter</A><DT>implements <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/Serializable.html?is-external=true" title="class or interface in java.io">Serializable</A></DL>
</PRE>

<P>
<p>
 File filter for matching files containing a "magic number". A magic number 
 is a unique series of bytes common to all files of a specific file format.
 For instance, all Java class files begin with the bytes 
 <code>0xCAFEBABE</code>. 
 </p>
 
 <code><pre>
 File dir = new File(".");
 MagicNumberFileFilter javaClassFileFilter =
     MagicNumberFileFilter(new byte[] {(byte) 0xCA, (byte) 0xFE, 
       (byte) 0xBA, (byte) 0xBE}); 
 String[] javaClassFiles = dir.list(javaClassFileFilter);
 for (String javaClassFile : javaClassFiles) {
     System.out.println(javaClassFile);
 }
 </pre></code>
 
 <p>
 Sometimes, such as in the case of TAR files, the
 magic number will be offset by a certain number of bytes in the file. In the
 case of TAR archive files, this offset is 257 bytes.
 </p>
 
 <code><pre>
 File dir = new File(".");
 MagicNumberFileFilter tarFileFilter = 
     MagicNumberFileFilter("ustar", 257); 
 String[] tarFiles = dir.list(tarFileFilter);
 for (String tarFile : tarFiles) {
     System.out.println(tarFile);
 }
 </pre></code>
<P>

<P>
<DL>
<DT><B>See Also:</B><DD><A HREF="../../../../../serialized-form.html#org.apache.commons.io.filefilter.MagicNumberFileFilter">Serialized Form</A></DL>
<HR>

<P>
<!-- =========== FIELD SUMMARY =========== -->

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<CODE>private &nbsp;long</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#byteOffset">byteOffset</A></B></CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The offset (in bytes) within the files that the magic number's bytes 
 should appear.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE>private &nbsp;byte[]</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#magicNumbers">magicNumbers</A></B></CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The magic number to compare against the file's bytes at the provided 
 offset.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE>private static&nbsp;long</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#serialVersionUID">serialVersionUID</A></B></CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The serialization version unique identifier.</TD>
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<!-- ======== CONSTRUCTOR SUMMARY ======== -->

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<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#MagicNumberFileFilter(byte[])">MagicNumberFileFilter</A></B>(byte[]&nbsp;magicNumber)</CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
 Constructs a new MagicNumberFileFilter and associates it with the magic
 number to test for in files.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#MagicNumberFileFilter(byte[], long)">MagicNumberFileFilter</A></B>(byte[]&nbsp;magicNumber,
                      long&nbsp;offset)</CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
 Constructs a new MagicNumberFileFilter and associates it with the magic
 number to test for in files and the byte offset location in the file to
 to look for that magic number.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#MagicNumberFileFilter(java.lang.String)">MagicNumberFileFilter</A></B>(<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A>&nbsp;magicNumber)</CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
 Constructs a new MagicNumberFileFilter and associates it with the magic
 number to test for in files.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#MagicNumberFileFilter(java.lang.String, long)">MagicNumberFileFilter</A></B>(<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A>&nbsp;magicNumber,
                      long&nbsp;offset)</CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
 Constructs a new MagicNumberFileFilter and associates it with the magic
 number to test for in files and the byte offset location in the file to
 to look for that magic number.</TD>
</TR>
</TABLE>
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<!-- ========== METHOD SUMMARY =========== -->

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<B>Method Summary</B></FONT></TH>
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<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE>&nbsp;boolean</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#accept(java.io.File)">accept</A></B>(<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/File.html?is-external=true" title="class or interface in java.io">File</A>&nbsp;file)</CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
 Accepts the provided file if the file contains the file filter's magic
 number at the specified offset.</TD>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE>&nbsp;<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../org/apache/commons/io/filefilter/MagicNumberFileFilter.html#toString()">toString</A></B>()</CODE>

<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a String representation of the file filter, which includes the 
 magic number bytes and byte offset.</TD>
</TR>
</TABLE>
&nbsp;<A NAME="methods_inherited_from_class_org.apache.commons.io.filefilter.AbstractFileFilter"><!-- --></A>
<TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY="">
<TR BGCOLOR="#EEEEFF" CLASS="TableSubHeadingColor">
<TH ALIGN="left"><B>Methods inherited from class org.apache.commons.io.filefilter.<A HREF="../../../../../org/apache/commons/io/filefilter/AbstractFileFilter.html" title="class in org.apache.commons.io.filefilter">AbstractFileFilter</A></B></TH>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD><CODE><A HREF="../../../../../org/apache/commons/io/filefilter/AbstractFileFilter.html#accept(java.io.File, java.lang.String)">accept</A></CODE></TD>
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&nbsp;<A NAME="methods_inherited_from_class_java.lang.Object"><!-- --></A>
<TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY="">
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<TH ALIGN="left"><B>Methods inherited from class java.lang.<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</A></B></TH>
</TR>
<TR BGCOLOR="white" CLASS="TableRowColor">
<TD><CODE><A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#clone()" title="class or interface in java.lang">clone</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#equals(java.lang.Object)" title="class or interface in java.lang">equals</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#finalize()" title="class or interface in java.lang">finalize</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#getClass()" title="class or interface in java.lang">getClass</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#hashCode()" title="class or interface in java.lang">hashCode</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#notify()" title="class or interface in java.lang">notify</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#notifyAll()" title="class or interface in java.lang">notifyAll</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#wait()" title="class or interface in java.lang">wait</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#wait(long)" title="class or interface in java.lang">wait</A>, <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Object.html?is-external=true#wait(long, int)" title="class or interface in java.lang">wait</A></CODE></TD>
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&nbsp;
<P>

<!-- ============ FIELD DETAIL =========== -->

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<A NAME="serialVersionUID"><!-- --></A><H3>
serialVersionUID</H3>
<PRE>
private static final long <B>serialVersionUID</B></PRE>
<DL>
<DD>The serialization version unique identifier.
<P>
<DL>
<DT><B>See Also:</B><DD><A HREF="../../../../../constant-values.html#org.apache.commons.io.filefilter.MagicNumberFileFilter.serialVersionUID">Constant Field Values</A></DL>
</DL>
<HR>

<A NAME="magicNumbers"><!-- --></A><H3>
magicNumbers</H3>
<PRE>
private final byte[] <B>magicNumbers</B></PRE>
<DL>
<DD>The magic number to compare against the file's bytes at the provided 
 offset.
<P>
<DL>
</DL>
</DL>
<HR>

<A NAME="byteOffset"><!-- --></A><H3>
byteOffset</H3>
<PRE>
private final long <B>byteOffset</B></PRE>
<DL>
<DD>The offset (in bytes) within the files that the magic number's bytes 
 should appear.
<P>
<DL>
</DL>
</DL>

<!-- ========= CONSTRUCTOR DETAIL ======== -->

<A NAME="constructor_detail"><!-- --></A>
<TABLE BORDER="1" WIDTH="100%" CELLPADDING="3" CELLSPACING="0" SUMMARY="">
<TR BGCOLOR="#CCCCFF" CLASS="TableHeadingColor">
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<B>Constructor Detail</B></FONT></TH>
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<A NAME="MagicNumberFileFilter(byte[])"><!-- --></A><H3>
MagicNumberFileFilter</H3>
<PRE>
public <B>MagicNumberFileFilter</B>(byte[]&nbsp;magicNumber)</PRE>
<DL>
<DD><p>
 Constructs a new MagicNumberFileFilter and associates it with the magic
 number to test for in files. This constructor assumes a starting offset
 of <code>0</code>.
 </p>
 
 <p>
 It is important to note that <em>the array is not cloned</em> and that
 any changes to the magic number array after construction will affect the
 behavior of this file filter.
 </p>
 
 <code><pre>
 MagicNumberFileFilter javaClassFileFilter =
     MagicNumberFileFilter(new byte[] {(byte) 0xCA, (byte) 0xFE, 
       (byte) 0xBA, (byte) 0xBE}); 
 </pre></code>
<P>
<DL>
<DT><B>Parameters:</B><DD><CODE>magicNumber</CODE> - the magic number to look for in the file.
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/IllegalArgumentException.html?is-external=true" title="class or interface in java.lang">IllegalArgumentException</A></CODE> - if <code>magicNumber</code> is 
         <code>null</code>, or contains no bytes.</DL>
</DL>
<HR>

<A NAME="MagicNumberFileFilter(java.lang.String)"><!-- --></A><H3>
MagicNumberFileFilter</H3>
<PRE>
public <B>MagicNumberFileFilter</B>(<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A>&nbsp;magicNumber)</PRE>
<DL>
<DD><p>
 Constructs a new MagicNumberFileFilter and associates it with the magic
 number to test for in files. This constructor assumes a starting offset
 of <code>0</code>.
 </p>
 
 Example usage:
 <pre>
 <code>MagicNumberFileFilter xmlFileFilter = 
     MagicNumberFileFilter("&lt;?xml"); 
 </code>
 </pre>
<P>
<DL>
<DT><B>Parameters:</B><DD><CODE>magicNumber</CODE> - the magic number to look for in the file.
        The string is converted to bytes using the platform default charset.
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/IllegalArgumentException.html?is-external=true" title="class or interface in java.lang">IllegalArgumentException</A></CODE> - if <code>magicNumber</code> is 
         <code>null</code> or the empty String.</DL>
</DL>
<HR>

<A NAME="MagicNumberFileFilter(java.lang.String, long)"><!-- --></A><H3>
MagicNumberFileFilter</H3>
<PRE>
public <B>MagicNumberFileFilter</B>(<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A>&nbsp;magicNumber,
                             long&nbsp;offset)</PRE>
<DL>
<DD><p>
 Constructs a new MagicNumberFileFilter and associates it with the magic
 number to test for in files and the byte offset location in the file to
 to look for that magic number.
 </p>
 
 <code><pre>
 MagicNumberFileFilter tarFileFilter = 
     MagicNumberFileFilter("ustar", 257); 
 </pre></code>
<P>
<DL>
<DT><B>Parameters:</B><DD><CODE>magicNumber</CODE> - the magic number to look for in the file. 
        The string is converted to bytes using the platform default charset.<DD><CODE>offset</CODE> - the byte offset in the file to start comparing bytes.
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/IllegalArgumentException.html?is-external=true" title="class or interface in java.lang">IllegalArgumentException</A></CODE> - if <code>magicNumber</code> is 
         <code>null</code> or the empty String, or <code>offset</code> is 
         a negative number.</DL>
</DL>
<HR>

<A NAME="MagicNumberFileFilter(byte[], long)"><!-- --></A><H3>
MagicNumberFileFilter</H3>
<PRE>
public <B>MagicNumberFileFilter</B>(byte[]&nbsp;magicNumber,
                             long&nbsp;offset)</PRE>
<DL>
<DD><p>
 Constructs a new MagicNumberFileFilter and associates it with the magic
 number to test for in files and the byte offset location in the file to
 to look for that magic number.
 </p>
 
 <p>
 It is important to note that <em>the array is not cloned</em> and that
 any changes to the magic number array after construction will affect the
 behavior of this file filter.
 </p>
 
 <code><pre>
 MagicNumberFileFilter tarFileFilter =
     MagicNumberFileFilter(new byte[] {0x75, 0x73, 0x74, 0x61, 0x72}, 257); 
 </pre></code>
 
 <code><pre>
 MagicNumberFileFilter javaClassFileFilter =
     MagicNumberFileFilter(new byte[] {0xCA, 0xFE, 0xBA, 0xBE}, 0); 
 </pre></code>
<P>
<DL>
<DT><B>Parameters:</B><DD><CODE>magicNumber</CODE> - the magic number to look for in the file.<DD><CODE>offset</CODE> - the byte offset in the file to start comparing bytes.
<DT><B>Throws:</B>
<DD><CODE><A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/IllegalArgumentException.html?is-external=true" title="class or interface in java.lang">IllegalArgumentException</A></CODE> - if <code>magicNumber</code> is 
         <code>null</code>, or contains no bytes, or <code>offset</code> 
         is a negative number.</DL>
</DL>

<!-- ============ METHOD DETAIL ========== -->

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<A NAME="accept(java.io.File)"><!-- --></A><H3>
accept</H3>
<PRE>
public boolean <B>accept</B>(<A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/File.html?is-external=true" title="class or interface in java.io">File</A>&nbsp;file)</PRE>
<DL>
<DD><p>
 Accepts the provided file if the file contains the file filter's magic
 number at the specified offset.
 </p>
 
 <p>
 If any <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/IOException.html?is-external=true" title="class or interface in java.io"><CODE>IOException</CODE></A>s occur while reading the file, the file will
 be rejected.
 </p>
<P>
<DD><DL>
<DT><B>Specified by:</B><DD><CODE><A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/FileFilter.html?is-external=true#accept(java.io.File)" title="class or interface in java.io">accept</A></CODE> in interface <CODE><A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/io/FileFilter.html?is-external=true" title="class or interface in java.io">FileFilter</A></CODE><DT><B>Specified by:</B><DD><CODE><A HREF="../../../../../org/apache/commons/io/filefilter/IOFileFilter.html#accept(java.io.File)">accept</A></CODE> in interface <CODE><A HREF="../../../../../org/apache/commons/io/filefilter/IOFileFilter.html" title="interface in org.apache.commons.io.filefilter">IOFileFilter</A></CODE><DT><B>Overrides:</B><DD><CODE><A HREF="../../../../../org/apache/commons/io/filefilter/AbstractFileFilter.html#accept(java.io.File)">accept</A></CODE> in class <CODE><A HREF="../../../../../org/apache/commons/io/filefilter/AbstractFileFilter.html" title="class in org.apache.commons.io.filefilter">AbstractFileFilter</A></CODE></DL>
</DD>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>file</CODE> - the file to accept or reject.
<DT><B>Returns:</B><DD><code>true</code> if the file contains the filter's magic number 
         at the specified offset, <code>false</code> otherwise.</DL>
</DD>
</DL>
<HR>

<A NAME="toString()"><!-- --></A><H3>
toString</H3>
<PRE>
public <A HREF="http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</A> <B>toString</B>()</PRE>
<DL>
<DD>Returns a String representation of the file filter, which includes the 
 magic number bytes and byte offset.
<P>
<DD><DL>
<DT><B>Overrides:</B><DD><CODE><A HREF="../../../../../org/apache/commons/io/filefilter/AbstractFileFilter.html#toString()">toString</A></CODE> in class <CODE><A HREF="../../../../../org/apache/commons/io/filefilter/AbstractFileFilter.html" title="class in org.apache.commons.io.filefilter">AbstractFileFilter</A></CODE></DL>
</DD>
<DD><DL>

<DT><B>Returns:</B><DD>a String representation of the file filter.</DL>
</DD>
</DL>
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