tij319.htm

这也是我们java老师给我们的thinking in java的一些资料

      e.printStackTrace();
    }
    <font color=#0000ff>return</font> o;
  }
  <font color=#0000ff>public</font> <font color=#0000ff>double</font> getTemperature() { <font color=#0000ff>return</font> temperature; }
  <font color=#0000ff>public</font> <font color=#0000ff>void</font> setTemperature(<font color=#0000ff>double</font> temperature) {
    <font color=#0000ff>this</font>.temperature = temperature;
  }
  <font color=#0000ff>public</font> String toString() {
    <font color=#0000ff>return</font> String.valueOf(temperature);
  }
}

<font color=#0000ff>class</font> OceanReading <font color=#0000ff>implements</font> Cloneable {
  <font color=#0000ff>private</font> DepthReading depth;
  <font color=#0000ff>private</font> TemperatureReading temperature;
  <font color=#0000ff>public</font> OceanReading(<font color=#0000ff>double</font> tdata, <font color=#0000ff>double</font> ddata) {
    temperature = <font color=#0000ff>new</font> TemperatureReading(tdata);
    depth = <font color=#0000ff>new</font> DepthReading(ddata);
  }
  <font color=#0000ff>public</font> Object clone() {
    OceanReading o = <font color=#0000ff>null</font>;
    <font color=#0000ff>try</font> {
      o = (OceanReading)<font color=#0000ff>super</font>.clone();
    } <font color=#0000ff>catch</font>(CloneNotSupportedException e) {
      e.printStackTrace();
    }
    <font color=#009900>// Must clone references:</font>
    o.depth = (DepthReading)o.depth.clone();
    o.temperature =
      (TemperatureReading)o.temperature.clone();
    <font color=#0000ff>return</font> o; <font color=#009900>// Upcasts back to Object</font>
  }
  <font color=#0000ff>public</font> TemperatureReading getTemperatureReading() {
    <font color=#0000ff>return</font> temperature;
  }
  <font color=#0000ff>public</font> <font color=#0000ff>void</font> setTemperatureReading(TemperatureReading tr){
    temperature = tr;
  }
  <font color=#0000ff>public</font> DepthReading getDepthReading() { <font color=#0000ff>return</font> depth; }
  <font color=#0000ff>public</font> <font color=#0000ff>void</font> setDepthReading(DepthReading dr) {
    <font color=#0000ff>this</font>.depth = dr;
  }
  <font color=#0000ff>public</font> String toString() {
    <font color=#0000ff>return</font> <font color=#004488>"temperature: "</font> + temperature +
      <font color=#004488>", depth: "</font> + depth;
  }
}

<font color=#0000ff>public</font> <font color=#0000ff>class</font> DeepCopy <font color=#0000ff>extends</font> TestCase {
  <font color=#0000ff>public</font> DeepCopy(String name) { <font color=#0000ff>super</font>(name); }
  <font color=#0000ff>public</font> <font color=#0000ff>void</font> testClone() {
    OceanReading reading = <font color=#0000ff>new</font> OceanReading(33.9, 100.5);
    <font color=#009900>// Now clone it:</font>
    OceanReading clone = (OceanReading)reading.clone();
    TemperatureReading tr = clone.getTemperatureReading();
    tr.setTemperature(tr.getTemperature() + 1);
    clone.setTemperatureReading(tr);
    DepthReading dr = clone.getDepthReading();
    dr.setDepth(dr.getDepth() + 1);
    clone.setDepthReading(dr);
    assertEquals(reading.toString(),
      <font color=#004488>"temperature: 33.9, depth: 100.5"</font>);
    assertEquals(clone.toString(),
      <font color=#004488>"temperature: 34.9, depth: 101.5"</font>);
  }
  <font color=#0000ff>public</font> <font color=#0000ff>static</font> <font color=#0000ff>void</font> main(String[] args) {
    junit.textui.TestRunner.run(DeepCopy.<font color=#0000ff>class</font>);
  }
} <font color=#009900>///:~</font></PRE></FONT></BLOCKQUOTE><p><br></p>
<p><b>DepthReading</b> and <b>TemperatureReading</b> are quite similar; they both contain only primitives. Therefore, the <b>clone(&#160;)</b> method can be quite simple: it calls <b>super.clone(&#160;)</b> and returns the result. Note that the <b>clone(&#160;)</b> code for both classes is identical. <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]AppendA_2730" title="Send BackTalk Comment">Feedback</a></font><br></p>
<p><b>OceanReading</b> is composed of <b>DepthReading</b> and <b>TemperatureReading</b> objects and so, to produce a deep copy, its <b>clone(&#160;)</b> must clone the references inside <b>OceanReading</b>. To accomplish this, the result of <b>super.clone(&#160;)</b> must be cast to an <b>OceanReading</b> object (so you can access the <b>depth</b> and <b>temperature</b> references). <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]AppendA_2731" title="Send BackTalk Comment">Feedback</a></font><br></p>
<h3>
<a name="_Toc24775998"></a><a name="Heading24904"></a>A deep copy with
<b>ArrayList</b></h3>
<p>Let&#146;s revisit <b>Cloning.java</b> from earlier in this appendix. This time the <b>Int2</b> class is cloneable, so the <b>ArrayList</b> can be deep copied:<br></p>

<BLOCKQUOTE><FONT SIZE = "+1"><PRE><font color=#009900>//: appendixa:AddingClone.java</font>
<font color=#009900>// You must go through a few gyrations</font>
<font color=#009900>// to add cloning to your own class.</font>
<font color=#0000ff>import</font> com.bruceeckel.simpletest.*;
<font color=#0000ff>import</font> java.util.*;

<font color=#0000ff>class</font> Int2 <font color=#0000ff>implements</font> Cloneable {
  <font color=#0000ff>private</font> <font color=#0000ff>int</font> i;
  <font color=#0000ff>public</font> Int2(<font color=#0000ff>int</font> ii) { i = ii; }
  <font color=#0000ff>public</font> <font color=#0000ff>void</font> increment() { i++; }
  <font color=#0000ff>public</font> String toString() { <font color=#0000ff>return</font> Integer.toString(i); }
  <font color=#0000ff>public</font> Object clone() {
    Object o = <font color=#0000ff>null</font>;
    <font color=#0000ff>try</font> {
      o = <font color=#0000ff>super</font>.clone();
    } <font color=#0000ff>catch</font>(CloneNotSupportedException e) {
      System.err.println(<font color=#004488>"Int2 can't clone"</font>);
    }
    <font color=#0000ff>return</font> o;
  }
}

<font color=#009900>// Inheritance doesn't remove cloneability:</font>
<font color=#0000ff>class</font> Int3 <font color=#0000ff>extends</font> Int2 {
  <font color=#0000ff>private</font> <font color=#0000ff>int</font> j; <font color=#009900>// Automatically duplicated</font>
  <font color=#0000ff>public</font> Int3(<font color=#0000ff>int</font> i) { <font color=#0000ff>super</font>(i); }
}

<font color=#0000ff>public</font> <font color=#0000ff>class</font> AddingClone {
  <font color=#0000ff>private</font> <font color=#0000ff>static</font> Test monitor = <font color=#0000ff>new</font> Test();
  <font color=#0000ff>public</font> <font color=#0000ff>static</font> <font color=#0000ff>void</font> main(String[] args) {
    Int2 x = <font color=#0000ff>new</font> Int2(10);
    Int2 x2 = (Int2)x.clone();
    x2.increment();
    System.out.println(<font color=#004488>"x = "</font> + x + <font color=#004488>", x2 = "</font> + x2);
    <font color=#009900>// Anything inherited is also cloneable:</font>
    Int3 x3 = <font color=#0000ff>new</font> Int3(7);
    x3 = (Int3)x3.clone();
    ArrayList v = <font color=#0000ff>new</font> ArrayList();
    <font color=#0000ff>for</font>(<font color=#0000ff>int</font> i = 0; i &lt; 10; i++ )
      v.add(<font color=#0000ff>new</font> Int2(i));
    System.out.println(<font color=#004488>"v: "</font> + v);
    ArrayList v2 = (ArrayList)v.clone();
    <font color=#009900>// Now clone each element:</font>
    <font color=#0000ff>for</font>(<font color=#0000ff>int</font> i = 0; i &lt; v.size(); i++)
      v2.set(i, ((Int2)v2.get(i)).clone());
    <font color=#009900>// Increment all v2's elements:</font>
    <font color=#0000ff>for</font>(Iterator e = v2.iterator(); e.hasNext(); )
      ((Int2)e.next()).increment();
    System.out.println(<font color=#004488>"v2: "</font> + v2);
    <font color=#009900>// See if it changed v's elements:</font>
    System.out.println(<font color=#004488>"v: "</font> + v);
    monitor.expect(<font color=#0000ff>new</font> String[] {
      <font color=#004488>"x = 10, x2 = 11"</font>,
      <font color=#004488>"v: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"</font>,
      <font color=#004488>"v2: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]"</font>,
      <font color=#004488>"v: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"</font>