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<!-- Generated by javadoc (1.8.0_151) on Tue Oct 31 17:36:52 EDT 2017 -->
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<title>StockQuotes (Oracle - Berkeley DB Java Edition Examples)</title>
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<div class="aboutLanguage"><b>Berkeley DB Java Edition Examples</b><br><font size=\"-1\"> version 7.5.11</font>
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<div class="subTitle">je.rep.quote</div>
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<h2 title="Class StockQuotes" class="title">Class StockQuotes</h2>
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<div class="contentContainer">
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<ul class="inheritance">
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<li>je.rep.quote.StockQuotes</li>
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<dl>
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<dt>Direct Known Subclasses:</dt>
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<dd><a href="../../../je/rep/quote/RouterDrivenStockQuotes.html" title="class in je.rep.quote">RouterDrivenStockQuotes</a>, <a href="../../../je/rep/quote/StockQuotesRMIForwarding.html" title="class in je.rep.quote">StockQuotesRMIForwarding</a></dd>
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</dl>
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<hr>
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<br>
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<pre>public class <span class="typeNameLabel">StockQuotes</span>
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extends java.lang.Object</pre>
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<div class="block">The most basic demonstration of a replicated application. It's intended to
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help gain an understanding of basic HA concepts and demonstrate use of the
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HA APIs to create a replicated environment and issue read and write
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transactions.
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<p>
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Be sure to read the <a href="../../../je/rep/quote/package-summary.html"><code>Example Overview</code></a> first to put this
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example into context.
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<p>
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The program can be used to start up multiple stock quote servers supplying
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the following arguments:
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<pre>
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java je.rep.quote.StockQuotes -env <environment home> \
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-nodeName <nodeName> \
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-nodeHost <hostname:port> \
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-helperHost <hostname:port>
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</pre>
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The argument names resemble the <a href="../../../../java/com/sleepycat/je/rep/ReplicationConfig.html?is-external=true" title="class or interface in com.sleepycat.je.rep"><code>ReplicationConfig</code></a> names to draw
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attention to the connection between the program argument names and
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ReplicationConfig APIs.
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<pre>
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-env a pre-existing directory for the replicated JE environment
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-nodeName the name used to uniquely identify this node in the replication
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-nodeHost the unique hostname, port pair for this node
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-helperHost the hostname, port pair combination for the helper node. It's
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the same as the nodeHost only if this node is intended to
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become the initial Master, during the formation of the
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replication group.
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</pre>
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A typical demo session begins with a set of commands such as the following
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to start each node. The first node can be started as below:
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<pre>
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java je.rep.quote.StockQuotes -env dir1 -nodeName n1 \
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-nodeHost node.acme.com:5001 \
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-helperHost node.acme.com:5001
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</pre>
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Note that the <code>helperHost</code> and the <code>nodeHost</code> are the
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same, since it's the first node in the group. HA uses this fact to start a
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brand new replication group of size one, with this node as the master if
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there is no existing environment in the environment directory
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<code>dir1</code>.
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<p>
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Nodes can be added to the group by using a variation of the above. The
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second and third node can be started as follows:
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<pre>
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java je.rep.quote.StockQuotes -env dir2 -nodeName n2 \
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-nodeHost node.acme.com:5002 \
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-helperHost node.acme.com:5001
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java je.rep.quote.StockQuotes -env dir3 -nodeName n3 \
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-nodeHost node.acme.com:5003 \
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-helperHost node.acme.com:5002
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</pre>
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Note that each node has its own unique node name, and a distinct directory
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for its replicated environment. This and any subsequent nodes can use the
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first node as a helper to get itself going. In fact, you can pick any node
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already in the group to serve as a helper. So, for example when adding the
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third node, node 2 or node 1, could serve as helper nodes. The helper nodes
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simply provide a mechanism to help a new node get itself admitted into the
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group. The helper node is not needed once a node becomes part of the group.
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<p>
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When initially running the example, please use a group of at least three
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nodes. A two node group is a special case, and it is best to learn how to
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run larger groups first. For more information, see
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<a href="../../../../ReplicationGuide/lifecycle.html#twonode">
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Two-Node Replication Groups</a>. When initially creating the nodes, it is
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also important to start the master first.
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<p>
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But once the nodes have been created, the order in which the nodes are
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started up does not matter. It minimizes the initial overall group startup
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time to have the master (the one where the <code>helperHost</code> and the
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<code>nodeHost</code> are the same) node started first, since the master
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initializes the replicated environment and is ready to start accepting and
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processing commands even as the other nodes concurrently join the group.
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<p>
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The above commands start up a group with three nodes all running locally on
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the same machine. You can start up nodes on different machines connected by
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a TCP/IP network by executing the above commands on the respective machines.
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It's important in this case that the clocks on these machines, be reasonably
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synchronized, that is, they should be within a couple of seconds of each
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other. You can do this manually, but it's best to use a protocol like <a
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href="http://www.ntp.org/">NTP</a> for this purpose.
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<p>
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Upon subsequent restarts the nodes will automatically hold an election and
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select one of the nodes in the group to be the master. The choice of master
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is made visible by the master/replica prompt that the application uses to
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make the distinction clear. Note that at least a simple majority of nodes
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must be started before the application will respond with a prompt because
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it's only after a simple majority of nodes is available that an election can
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be held and a master elected. For a two node group, both nodes must be
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started before an election can be held.
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<p>
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Commands are submitted directly at the command prompt in the console
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established by the application at each node. Update commands are only
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accepted at the console associated with the current master, identified by
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the <i>master</i> prompt as below:
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<pre>StockQuotes-2 (master)></pre>
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After issuing a few commands, you may want to experiment with shutting down
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or killing some number of the replicated environments and bringing them back
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up to see how the application behaves.
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<p>
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If you type stock updates at an application that is currently running as a
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replica node, the update is refused and you must manually re-enter the
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updates on the console associated with the master. This is of course quite
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cumbersome and serves as motivation for the subsequent examples.
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<p>
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As shown below, there is no routing of requests between nodes in this
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example, which is why write requests fail when they are issued on a Replica
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node.
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<pre>
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-----------------------
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| StockQuotes | Read and Write requests both succeed,
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| Instance 1: Master | because this is the Master.
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-----------------------
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-----------------------
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| StockQuotes | Read requests succeed,
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| Instance 2: Replica | but Write requests fail on a Replica.
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-----------------------
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-----------------------
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| StockQuotes | Read requests succeed,
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| Instance 3: Replica | but Write requests fail on a Replica.
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-----------------------
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...more Replica instances...
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</pre>
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<p>
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See <a href="../../../je/rep/quote/UpdateForwardingStockQuotes.html" title="class in je.rep.quote"><code>UpdateForwardingStockQuotes</code></a> for an example that uses
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<a href="../../../je/rep/quote/SimpleRouter.html" title="class in je.rep.quote"><code>SimpleRouter</code></a>, along with application supplied inter-node request
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routing to direct write requests to the master.
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<p>
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See <a href="../../../je/rep/quote/RouterDrivenStockQuotes.html" title="class in je.rep.quote"><code>RouterDrivenStockQuotes</code></a> along with <a href="../../../je/rep/quote/HARouter.html" title="class in je.rep.quote"><code>HARouter</code></a>for an
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example that uses an external router built using the
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<a href="../../../../java/com/sleepycat/je/rep/monitor/Monitor.html?is-external=true" title="class or interface in com.sleepycat.je.rep.monitor"><code>Monitor</code></a> to route write
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requests externally to the master and provide primitive load balancing
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across the nodes in the replication group.</div>
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</li>
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</ul>
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</div>
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<div class="summary">
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<ul class="blockList">
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<li class="blockList">
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<!-- ========== METHOD SUMMARY =========== -->
|
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<ul class="blockList">
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<li class="blockList"><a name="method.summary">
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<!-- -->
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</a>
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<h3>Method Summary</h3>
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<table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Method Summary table, listing methods, and an explanation">
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<caption><span id="t0" class="activeTableTab"><span>All Methods</span><span class="tabEnd"> </span></span><span id="t1" class="tableTab"><span><a href="javascript:show(1);">Static Methods</a></span><span class="tabEnd"> </span></span><span id="t2" class="tableTab"><span><a href="javascript:show(2);">Instance Methods</a></span><span class="tabEnd"> </span></span><span id="t4" class="tableTab"><span><a href="javascript:show(8);">Concrete Methods</a></span><span class="tabEnd"> </span></span></caption>
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<tr>
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<th class="colFirst" scope="col">Modifier and Type</th>
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<th class="colLast" scope="col">Method and Description</th>
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</tr>
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<tr id="i0" class="altColor">
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<td class="colFirst"><code>static void</code></td>
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<td class="colLast"><code><span class="memberNameLink"><a href="../../../je/rep/quote/StockQuotes.html#main-java.lang.String:A-">main</a></span>(java.lang.String[] argv)</code> </td>
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</tr>
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<tr id="i1" class="rowColor">
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<td class="colFirst"><code>void</code></td>
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<td class="colLast"><code><span class="memberNameLink"><a href="../../../je/rep/quote/StockQuotes.html#quit-java.io.PrintStream-">quit</a></span>(java.io.PrintStream out)</code>
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<div class="block">Implements the "quit" command.</div>
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</td>
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</tr>
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|
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</table>
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|
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<ul class="blockList">
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<li class="blockList"><a name="methods.inherited.from.class.java.lang.Object">
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<!-- -->
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|
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</a>
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||
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<h3>Methods inherited from class java.lang.Object</h3>
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||
|
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<code>equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait</code></li>
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|
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</ul>
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</li>
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</ul>
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</li>
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</ul>
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</div>
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<div class="details">
|
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|
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<ul class="blockList">
|
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<li class="blockList">
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|
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<!-- ============ METHOD DETAIL ========== -->
|
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<ul class="blockList">
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<li class="blockList"><a name="method.detail">
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|
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<!-- -->
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</a>
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<h3>Method Detail</h3>
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||
|
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<a name="quit-java.io.PrintStream-">
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<!-- -->
|
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</a>
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<ul class="blockList">
|
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<li class="blockList">
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<h4>quit</h4>
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<pre>public void quit(java.io.PrintStream out)</pre>
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<div class="block">Implements the "quit" command. Subclasses can override to take
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throws java.lang.Exception</pre>
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<dl>
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<dt><span class="throwsLabel">Throws:</span></dt>
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