?? coll_sets.html
字號:
<HTML>
<HEAD>
<META http-equiv="Content-Type" content="text/html; charset=UTF-8">
<TITLE>Creating a Set
(Java Developers Almanac Example)
</TITLE>
<META CONTENT="Patrick Chan" NAME="AUTHOR">
<META CONTENT="Code Examples from The Java Developers Almanac 1.4" NAME="DESCRIPTION">
<META CONTENT="Addison-Wesley/Patrick Chan" NAME="OWNER">
<META CONTENT="3/20/02" NAME="revision">
<STYLE TYPE="text/css">
<!-- BODY CODE {font-family: Courier, Monospace; font-size: 11pt} TABLE, BODY {font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 10pt} PRE {font-family: Courier, Monospace; font-size: 10pt} H3 {font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 11pt} A.eglink {text-decoration: none} A:hover.eglink {text-decoration: underline} -->
</STYLE>
</HEAD>
<BODY>
<TABLE CELLSPACING="0" CELLPADDING="0" BORDER="0">
<TR>
<TD rowspan="3"><A HREF="/?l=ex"><IMG BORDER="0" ALIGN="BOTTOM" HSPACE="10" SRC="/egs/almanac14a.jpg"></A></TD><TD VALIGN="top"><font face="Times" size="6"><b>The Java Developers Almanac 1.4</b></font>
<br>
Order this book from <a href="/cgi-bin/scripts/redirect.pl?l=ex&url=http://www.amazon.com/exec/obidos/ASIN/0201752808/xeo">Amazon</a>.
</TD>
</TR>
<TR>
<TD align="right" valign="bottom">
<FORM method="get" action="/cgi-bin/search/find.pl">
<INPUT size="25" name="words" type="text"><INPUT value="Search" type="submit">
</FORM>
</TD>
</TR>
</TABLE>
<HR color="#6666cc">
<DIV ALIGN="LEFT">
<A HREF="/">Home</A>
>
<A HREF="../index.html">List of Packages</A>
>
<B><A HREF="../java.util/pkg.html">java.util</A></B><font color="#666666" SIZE="-2">
[49 examples]
</font>
>
<B><A HREF="../java.util/pkg.html#Sets">Sets</A></B><font color="#666666" SIZE="-2">
[3 examples]
</font>
</DIV><P>
<h3>
e352.
Creating a Set</h3>
A set is a collection that holds unique values. Adding a value that's
already in the set has no effect.
<pre>
// Create the set
Set set = new HashSet();
// Add elements to the set
set.add(<font color="#0066ff"><i>"a"</i></font>);
set.add(<font color="#0066ff"><i>"b"</i></font>);
set.add(<font color="#0066ff"><i>"c"</i></font>);
// Remove elements from the set
set.remove(<font color="#0066ff"><i>"c"</i></font>);
// Get number of elements in set
int size = set.size(); // 2
// Adding an element that already exists in the set has no effect
set.add(<font color="#0066ff"><i>"a"</i></font>);
size = set.size(); // 2
// Determining if an element is in the set
boolean b = set.contains(<font color="#0066ff"><i>"a"</i></font>); // true
b = set.contains(<font color="#0066ff"><i>"c"</i></font>); // false
// Iterating over the elements in the set
Iterator it = set.iterator();
while (it.hasNext()) {
// Get element
Object element = it.next();
}
// Create an array containing the elements in the set (in this case a String array)
<font color="#0066ff"><i>String</i></font>[] array = (<font color="#0066ff"><i>String</i></font>[])set.toArray(new <font color="#0066ff"><i>String</i></font>[set.size()]);
</pre>
<P><table width="600" CELLSPACING="0" CELLPADDING="2" BORDER="0">
<tr>
<td bgcolor="#6666cc" align="center"><font color="#ffffff">
Related Examples
</font></td>
</tr>
</table>
e353. <a class="eglink" href="coll_SetOps.html?l=rel">
Operating on Sets
</a>
<br>
e354. <a class="eglink" href="coll_SetOrder.html?l=rel">
Creating a Set That Retains Order-of-Insertion
</a>
<br>
<table width="600" CELLSPACING="0" CELLPADDING="2" BORDER="0">
<tr>
<td align="left">
<br>
See also:
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Arrays">
Arrays
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Bits">
Bits
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Collections">
Collections
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Dates">
Dates
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Hash%20Tables">
Hash Tables
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Lists">
Lists
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Property%20Files">
Property Files
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Sorted%20Collections">
Sorted Collections
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Time">
Time
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Timers">
Timers
</a>
</td>
</tr>
</table>
<br>
<br>
<FONT FACE="Verdana, Arial, Helvetica, sans-serif" SIZE="0">
© 2002 Addison-Wesley.
</FONT>
</BODY>
</HTML>
?? 快捷鍵說明
復制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -