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e21cbe82a9
Where possible update Java documentation links to Java 11. Additionally update some other links to use HTTPS.
65 lines
2.1 KiB
XML
65 lines
2.1 KiB
XML
<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>
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The classes <code>java.io.OutputStream</code>
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and <code>java.io.FilterOutputStream</code> only require
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subclasses to implement the method <code>write(byte b)</code>.
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Typically, uses of <code>OutputStream</code>s will not write
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single bytes, but an array via the <code>write(byte[] b, int off,
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int len)</code> method. The default implementation of this method,
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which you are not required to override,
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calls <code>write(byte b)</code> for each byte in the array. If
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this method involves I/O, such as accessing the network or disk,
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this is likely to incur significant overhead.
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</p>
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</overview>
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<recommendation>
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<p>
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Always provide an implementation of the <code>write(byte[] b, int
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off, int len)</code> method.
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</p>
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</recommendation>
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<example>
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<p>
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The following example shows a subclass
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of <code>OutputStream</code> that simply wraps
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a <code>DigestOutputStream</code> to confirm that the data it
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writes to a file has the expected MD5 hash. Without an
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implementation of <code>write(byte[] b, int off, int len)</code>
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this will be very slow, because it makes a call
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to <code>DigestOutputStream.write(byte b)</code>
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and <code>FileOutputStream.write(byte b)</code> for each byte
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written.
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</p>
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<sample src="InefficientOutputStreamBad.java" />
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<p>
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The example can be updated to use a more efficient method. In this
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case, calls to <code>write(byte[] b, int off, int len)</code> are
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simply forwarded to <code>DigestOutputStream.write(byte[] b, int
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off, int len)</code>.
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</p>
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<sample src="InefficientOutputStreamGood.java" />
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</example>
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<references>
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<li>
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Java API Specification:
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<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/OutputStream.html#write(byte[],int,int)">OutputStream.write(byte[] b, int off, int len)</a>,
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<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/FilterOutputStream.html#write(byte[],int,int)">FilterOutputStream.write(byte[] b, int off, int len)</a>.
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</li>
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</references>
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</qhelp>
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