tij305.htm

这也是我们java老师给我们的thinking in java的一些资料

<font color=#0000ff>import</font> java.util.*;

<font color=#0000ff>public</font> <font color=#0000ff>class</font> BitManipulation {
  <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) {
    Random rand = <font color=#0000ff>new</font> Random();
    <font color=#0000ff>int</font> i = rand.nextInt();
    <font color=#0000ff>int</font> j = rand.nextInt();
    printBinaryInt(<font color=#004488>"-1"</font>, -1);
    printBinaryInt(<font color=#004488>"+1"</font>, +1);
    <font color=#0000ff>int</font> maxpos = 2147483647;
    printBinaryInt(<font color=#004488>"maxpos"</font>, maxpos);
    <font color=#0000ff>int</font> maxneg = -2147483648;
    printBinaryInt(<font color=#004488>"maxneg"</font>, maxneg);
    printBinaryInt(<font color=#004488>"i"</font>, i);
    printBinaryInt(<font color=#004488>"~i"</font>, ~i);
    printBinaryInt(<font color=#004488>"-i"</font>, -i);
    printBinaryInt(<font color=#004488>"j"</font>, j);
    printBinaryInt(<font color=#004488>"i &amp; j"</font>, i &amp; j);
    printBinaryInt(<font color=#004488>"i | j"</font>, i | j);
    printBinaryInt(<font color=#004488>"i ^ j"</font>, i ^ j);
    printBinaryInt(<font color=#004488>"i &lt;&lt; 5"</font>, i &lt;&lt; 5);
    printBinaryInt(<font color=#004488>"i &gt;&gt; 5"</font>, i &gt;&gt; 5);
    printBinaryInt(<font color=#004488>"(~i) &gt;&gt; 5"</font>, (~i) &gt;&gt; 5);
    printBinaryInt(<font color=#004488>"i &gt;&gt;&gt; 5"</font>, i &gt;&gt;&gt; 5);
    printBinaryInt(<font color=#004488>"(~i) &gt;&gt;&gt; 5"</font>, (~i) &gt;&gt;&gt; 5);

    <font color=#0000ff>long</font> l = rand.nextLong();
    <font color=#0000ff>long</font> m = rand.nextLong();
    printBinaryLong(<font color=#004488>"-1L"</font>, -1L);
    printBinaryLong(<font color=#004488>"+1L"</font>, +1L);
    <font color=#0000ff>long</font> ll = 9223372036854775807L;
    printBinaryLong(<font color=#004488>"maxpos"</font>, ll);
    <font color=#0000ff>long</font> lln = -9223372036854775808L;
    printBinaryLong(<font color=#004488>"maxneg"</font>, lln);
    printBinaryLong(<font color=#004488>"l"</font>, l);
    printBinaryLong(<font color=#004488>"~l"</font>, ~l);
    printBinaryLong(<font color=#004488>"-l"</font>, -l);
    printBinaryLong(<font color=#004488>"m"</font>, m);
    printBinaryLong(<font color=#004488>"l &amp; m"</font>, l &amp; m);
    printBinaryLong(<font color=#004488>"l | m"</font>, l | m);
    printBinaryLong(<font color=#004488>"l ^ m"</font>, l ^ m);
    printBinaryLong(<font color=#004488>"l &lt;&lt; 5"</font>, l &lt;&lt; 5);
    printBinaryLong(<font color=#004488>"l &gt;&gt; 5"</font>, l &gt;&gt; 5);
    printBinaryLong(<font color=#004488>"(~l) &gt;&gt; 5"</font>, (~l) &gt;&gt; 5);
    printBinaryLong(<font color=#004488>"l &gt;&gt;&gt; 5"</font>, l &gt;&gt;&gt; 5);
    printBinaryLong(<font color=#004488>"(~l) &gt;&gt;&gt; 5"</font>, (~l) &gt;&gt;&gt; 5);
    monitor.expect(<font color=#004488>"BitManipulation.out"</font>);
  }
  <font color=#0000ff>static</font> <font color=#0000ff>void</font> printBinaryInt(String s, <font color=#0000ff>int</font> i) {
    System.out.println(
      s + <font color=#004488>", int: "</font> + i + <font color=#004488>", binary: "</font>);
    System.out.print(<font color=#004488>"   "</font>);
    <font color=#0000ff>for</font>(<font color=#0000ff>int</font> j = 31; j &gt;= 0; j--)
      <font color=#0000ff>if</font>(((1 &lt;&lt; j) &amp;  i) != 0)
        System.out.print(<font color=#004488>"1"</font>);
      <font color=#0000ff>else</font>
        System.out.print(<font color=#004488>"0"</font>);
    System.out.println();
  }
  <font color=#0000ff>static</font> <font color=#0000ff>void</font> printBinaryLong(String s, <font color=#0000ff>long</font> l) {
    System.out.println(
      s + <font color=#004488>", long: "</font> + l + <font color=#004488>", binary: "</font>);
    System.out.print(<font color=#004488>"   "</font>);
    <font color=#0000ff>for</font>(<font color=#0000ff>int</font> i = 63; i &gt;= 0; i--)
      <font color=#0000ff>if</font>(((1L &lt;&lt; i) &amp; l) != 0)
        System.out.print(<font color=#004488>"1"</font>);
      <font color=#0000ff>else</font>
        System.out.print(<font color=#004488>"0"</font>);
    System.out.println();
  }
} <font color=#009900>///:~</font></PRE></FONT></BLOCKQUOTE><p><br></p>
<p><a name="Index245"></a>The two methods at the end, <b>printBinaryInt(&#160;)</b> and <b>printBinaryLong(&#160;)</b>, take an <b>int</b> or a <b>long</b>, respectively, and print it out in binary format along with a descriptive string. You can ignore the implementation of these for now. <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]Chap03_553" title="Send BackTalk Comment">Feedback</a></font><br></p>
<p>You&#146;ll note the use of <b>System.out.print(&#160;)</b> instead of <b>System.out.println(&#160;)</b>. The <b>print(&#160;)</b> method does not emit a newline, so it allows you to output a line in pieces. <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]Chap03_554" title="Send BackTalk Comment">Feedback</a></font><br></p>
<p>In this case, the <b>expect(&#160;)</b> statement takes a file name, from which it reads the expected lines (which may or may not include regular expressions). This is useful in situations where the output is too long or inappropriate to include in the book. The files ending with &#147;.out&#148; are part of the code distribution, available for download from <i>www.BruceEckel.com</i>, so you can open the file and look at it to see what the output should be (or simply run the program yourself). <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]A0457" title="Send BackTalk Comment">Feedback</a></font><br></p>
<p>As well as demonstrating the effect of all the bitwise operators for <b>int</b> and <b>long</b>, this example also shows the minimum, maximum, +1, and -1 values for <b>int</b> and <b>long</b> so you can see what they look like. Note that the high bit represents the sign: 0 means positive and 1 means negative. The output for the <b>int</b> portion looks like this:<br></p>

<BLOCKQUOTE><FONT SIZE = "+1"><PRE>-1, <font color=#0000ff>int</font>: -1, binary: 
   11111111111111111111111111111111
+1, <font color=#0000ff>int</font>: 1, binary: 
   00000000000000000000000000000001
maxpos, <font color=#0000ff>int</font>: 2147483647, binary: 
   01111111111111111111111111111111
maxneg, <font color=#0000ff>int</font>: -2147483648, binary: 
   10000000000000000000000000000000
i, <font color=#0000ff>int</font>: 59081716, binary: 
   00000011100001011000001111110100
~i, <font color=#0000ff>int</font>: -59081717, binary: 
   11111100011110100111110000001011
-i, <font color=#0000ff>int</font>: -59081716, binary: 
   11111100011110100111110000001100
j, <font color=#0000ff>int</font>: 198850956, binary: 
   00001011110110100011100110001100
i &amp; j, <font color=#0000ff>int</font>: 58720644, binary: 
   00000011100000000000000110000100
i | j, <font color=#0000ff>int</font>: 199212028, binary: 
   00001011110111111011101111111100
i ^ j, <font color=#0000ff>int</font>: 140491384, binary: 
   00001000010111111011101001111000
i &lt;&lt; 5, <font color=#0000ff>int</font>: 1890614912, binary: 
   01110000101100000111111010000000
i &gt;&gt; 5, <font color=#0000ff>int</font>: 1846303, binary: 
   00000000000111000010110000011111
(~i) &gt;&gt; 5, <font color=#0000ff>int</font>: -1846304, binary: 
   11111111111000111101001111100000
i &gt;&gt;&gt; 5, <font color=#0000ff>int</font>: 1846303, binary: 
   00000000000111000010110000011111
(~i) &gt;&gt;&gt; 5, <font color=#0000ff>int</font>: 132371424, binary: 
   00000111111000111101001111100000</PRE></FONT></BLOCKQUOTE><p><br></p>
<p>The binary representation of the numbers is referred to as <a name="Index246"></a><a name="Index247"></a><i>signed two&#146;s complement</i>. <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]Chap03_555" title="Send BackTalk Comment">Feedback</a></font><br></p>
<h3>
<a name="_Toc375545256"></a><a name="_Toc24775580"></a><a name="Heading2267"></a>Ternary
if-else operator</h3>
<p><a name="Index248"></a><a name="Index249"></a><a name="Index250"></a>This operator is unusual because it has three operands. It is truly an operator because it produces a value, unlike the ordinary if-else statement that you&#146;ll see in the next section of this chapter. The expression is of the form: <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]Chap03_556" title="Send BackTalk Comment">Feedback</a></font><br></p>

<BLOCKQUOTE><FONT SIZE = "+1"><PRE><font color=#0000ff>boolean</font>-exp ? value0 : value1</PRE></FONT></BLOCKQUOTE><p><br></p>