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<TITLE>Reading a File into a Byte Array (Java Developers Almanac Example)
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  <h3>e36. Reading a File into a Byte Array</h3>

This example implements a method that reads the entire contents of a
file into a byte array.

<P> See also <a href="../java.io/ReadLinesFromFile.html" class="eglink"><b>e35</b> Reading Text from a File</a>.


<pre>    // Returns the contents of the file in a byte array.
    public static byte[] getBytesFromFile(File file) throws IOException {
        InputStream is = new FileInputStream(file);
    
        // Get the size of the file
        long length = file.length();
    
        // You cannot create an array using a long type.
        // It needs to be an int type.
        // Before converting to an int type, check
        // to ensure that file is not larger than Integer.MAX_VALUE.
        if (length &gt; Integer.MAX_VALUE) {
            // File is too large
        }
    
        // Create the byte array to hold the data
        byte[] bytes = new byte[(int)length];
    
        // Read in the bytes
        int offset = 0;
        int numRead = 0;
        while (offset &lt; bytes.length
               &amp;&amp; (numRead=is.read(bytes, offset, bytes.length-offset)) &gt;= 0) {
            offset += numRead;
        }
    
        // Ensure all the bytes have been read in
        if (offset &lt; bytes.length) {
            throw new IOException("Could not completely read file "+file.getName());
        }
    
        // Close the input stream and return bytes
        is.close();
        return bytes;
    }
</pre>
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e34. <a class="eglink" href="ReadFromStdIn.html?l=rel">
    Reading Text from Standard Input
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e35. <a class="eglink" href="ReadLinesFromFile.html?l=rel">
    Reading Text from a File
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e37. <a class="eglink" href="WriteToFile.html?l=rel">
    Writing to a File
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e38. <a class="eglink" href="AppendToFile.html?l=rel">
    Appending to a File
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e39. <a class="eglink" href="UseRandomAccessFile.html?l=rel">
    Using a Random Access File
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