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<a href="http://www.bruceeckel.com/javabook.html">Bruce Eckel's Thinking in Java</a>
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<H2 ALIGN=LEFT>
Check
boxes
</H2>
<DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">A
check box provides a way to make a single on-off choice; it consists of a tiny
box and a label. The box typically holds a little &#8216;x&#8217; (or some
other indication that it is set) or is empty depending on whether that item was
selected.
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">You&#8217;ll
normally create a <A NAME="Index1633"></A><A NAME="Index1634"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Checkbox</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
using a constructor that takes the label as an argument. You can get and set
the state, and also get and set the label if you want to read or change it
after the 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Checkbox</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
has been created. Note that the capitalization of 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Checkbox</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
is inconsistent with the other controls, which could catch you by surprise
since you might expect it to be &#8220;CheckBox.&#8221;
</FONT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">Whenever
a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Checkbox</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
is set or cleared an event occurs, which you can capture the same way you do a
button. The following example uses a 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>TextArea</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
to enumerate all the check boxes that have been checked:
</FONT><P></DIV>

<font color="#990000"><PRE><font color="#009900">//: CheckBox1.java</font>
<font color="#009900">// Using check boxes</font>
<font color="#0000ff">import</font> java.awt.*;
<font color="#0000ff">import</font> java.applet.*;

<font color="#0000ff">public</font> <font color="#0000ff">class</font> CheckBox1 <font color="#0000ff">extends</font> Applet {
  TextArea t = <font color="#0000ff">new</font> TextArea(6, 20);
  Checkbox cb1 = <font color="#0000ff">new</font> Checkbox("Check Box 1");
  Checkbox cb2 = <font color="#0000ff">new</font> Checkbox("Check Box 2");
  Checkbox cb3 = <font color="#0000ff">new</font> Checkbox("Check Box 3");
  <font color="#0000ff">public</font> <font color="#0000ff">void</font> init() {
    add(t); add(cb1); add(cb2); add(cb3);
  }
  <font color="#0000ff">public</font> <font color="#0000ff">boolean</font> action (Event evt, Object arg) {
    <font color="#0000ff">if</font>(evt.target.equals(cb1))
      trace("1", cb1.getState());
    <font color="#0000ff">else</font> <font color="#0000ff">if</font>(evt.target.equals(cb2))
      trace("2", cb2.getState());
    <font color="#0000ff">else</font> <font color="#0000ff">if</font>(evt.target.equals(cb3))
      trace("3", cb3.getState());
    <font color="#0000ff">else</font> 
      <font color="#0000ff">return</font> <font color="#0000ff">super</font>.action(evt, arg);
    <font color="#0000ff">return</font> <font color="#0000ff">true</font>;
  }
  <font color="#0000ff">void</font> trace(String b, <font color="#0000ff">boolean</font> state) {
    <font color="#0000ff">if</font>(state)
      t.appendText("Box " + b + " Set\n");
    <font color="#0000ff">else</font>
      t.appendText("Box " + b + " Cleared\n");
  }
} <font color="#009900">///:~ </PRE></font></font><DIV ALIGN=LEFT><P></DIV><DIV ALIGN=LEFT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">The
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>trace(&#160;)</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
method sends the name of the selected 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>Checkbox</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
and its current state to the 
</FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>TextArea</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
using <A NAME="Index1635"></A><A NAME="Index1636"></A></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black"><B>appendText(&#160;)</B></FONT><FONT FACE="Carmina Md BT" SIZE=3 COLOR="Black">
so you&#8217;ll see a cumulative list of the checkboxes that were selected and
what their state is.
</FONT><a name="_Toc375545453"></a><a name="_Toc408018689"></a><P></DIV>

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