多按钮切换页面

<script type="text/javascript">
function java(){
 var java = document.getElementById("java");
 var dt = document.getElementById("datastructure");
 var db = document.getElementById("database");

 java.style.display="block";
 dt.style.display="none";
 db.style.display="none";
}

function dt(){
 var java = document.getElementById("java");
 var dt = document.getElementById("datastructure");
 var db = document.getElementById("database");

 dt.style.display="block";
 java.style.display="none";
 db.style.display="none";
}

function db(){
 var java = document.getElementById("java");
 var dt = document.getElementById("datastructure");
 var db = document.getElementById("database");

 db.style.display="block";
 java.style.display="none";
 dt.style.display="none";
}
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<p>&nbsp;</p>
<p>&nbsp;</p>
<div>
<form>
    <input type="button" value="basic" onclick="java();" /> <input type="button" value="servlet" onclick="dt();" /> <input type="button" value="none" onclick="db();" />
</form>
</div>
<div style="display: block;" id="java">
<p>1<a href="http://www.javaworld.com/javaworld/javatips/jw-javatip75.html?page=1">Use nested classes for better organization</a></p>
</div>
<div style="display: none;" id="datastructure"><a href="http://www.zz172.com/tech/soft_pro/java-online/12066.html">1 深入研究Servlet线程安全性问题(好文)</a><br />
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</div>
<div style="display: none;" id="database">none </div>