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卡耐基课程练习

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<td width="5"><br></td>  <td class="td0_x" align="left" valign="top"> <h2 align="center">Using Arrays</h2>

 
<h3>Prerequisites, Goals, and Outcomes</h3>
<blockquote> <b><i>Prerequisites:</i></b> Before you begin this exercise, you 
  need mastery of the following: 
  <ul>
    <li> <em>Arrays</em>
<ul>
        <li>Knowledge of arrays
<ul>
            <li>Declaring arrays</li>

            <li>Initializing arrays</li>
            <li>Accessing array elements</li>
            <li>Using for-loops to process arrays</li>
          </ul>
        </li>
      </ul>
  </li></ul>

  <p> <b><i>Goals:</i></b> Reinforce your ability to use arrays
</p><p> <b><i>Outcomes:</i></b> You 
    will demonstrate mastery of the following: 
  </p><ul>
    <li>Using arrays
<ul>
        <li>Creating arrays
<ul>
            <li>From a set of  objects </li>

            <li>From another array</li>
          </ul>
        </li>
        <li>Processing arrays
<ul>
            <li>Finding an array element with a specific characteristic 
            </li><li>Counting the number of array elements with a specific characteristic 
            </li><li>Invoking a method on each array element 
            </li><li>Finding the string representation of an array</li>
          </ul>

        </li>
      </ul>
    </li>
  </ul>
</blockquote>
<h3>Background </h3>

<p> This assignment asks you to implement a set of methods that handle arrays.</p>
<h3>Description</h3>

<p>In this assignment, you will finish the implementation of <code>EmployeeArray</code>, 
  a class with static methods for creating, analyzing, and manipulating arrays 
  of <code>Employee</code> objects. iCarnegie provides a test driver and the class 
  <code>Employee</code>.</p>
<h4>Class <code>Employee</code></h4>
<p>A complete implementation of this class is included in the student
  archive <cite><a href="/content/SSD/SSD3/4.2.0.1/normal/pg-class-imp/pg-collctns/assm-qz-pr-arrays/pool-pr-arrays/qn-pr-arrays-empl/handout/student-files.zip"><code>student-files.zip</code></a></cite>. 
  Stop <em>now</em> and review its documentation:</p>

<ul>
  <li><a href="/content/SSD/SSD3/4.2.0.1/normal/pg-class-imp/pg-collctns/assm-qz-pr-arrays/pool-pr-arrays/qn-pr-arrays-empl/handout/Employee.html" target="externalWindow"><code><em>Employee.html</em></code></a>. 
    Documentation for class <code>Employee</code></li>
</ul>
<h4>Class <code>EmployeeArray</code></h4>
<p>A partial implementation of this class is included in the student archive <cite><a href="/content/SSD/SSD3/4.2.0.1/normal/pg-class-imp/pg-collctns/assm-qz-pr-arrays/pool-pr-arrays/qn-pr-arrays-empl/handout/student-files.zip"><code>student-files.zip</code></a></cite>. 
  You should complete the implementation of every method in this class. </p>
<h4>Class <code>TestEmployeeArray</code></h4>

<p>This class is a test driver for class <code>EmployeeArray</code>. It contains 
  test cases for every method in the class. A complete implementation is included 
  in the student archive <cite><a href="/content/SSD/SSD3/4.2.0.1/normal/pg-class-imp/pg-collctns/assm-qz-pr-arrays/pool-pr-arrays/qn-pr-arrays-empl/handout/student-files.zip"><code>student-files.zip</code></a></cite>. 
  You should use this class to test your implementation of <code>EmployeeArray</code>.</p>
<h3>Files</h3>
The following files are needed to complete this assignment: 
<ul>
  <li><cite><a href="/content/SSD/SSD3/4.2.0.1/normal/pg-class-imp/pg-collctns/assm-qz-pr-arrays/pool-pr-arrays/qn-pr-arrays-empl/handout/student-files.zip"><code>student-files.zip</code></a></cite>. 
    Download this file. This archive contains the following: 
    <ul>
      <li><cite><code>Employee.java</code></cite>. A complete implementation</li>

      <li> <cite><code>EmployeeArray.java</code></cite>. Use this template to 
        complete your implementation.</li>
      <li><cite><code>TestEmployeeArray.java</code></cite>. A complete implementation</li>
    </ul>
  </li>
</ul>
<h3>Tasks </h3>
<p>Implement all methods in class <code>EmployeeArray</code>. Follow Sun's code 
  conventions. The following steps will guide you through this assignment. Work 
  incrementally and test each increment. Save often.</p>

<ol start="1">
  <li><strong>Extract </strong> the files by issuing the following command at 
    the command prompt: 
    <p><tt>C:\&gt;</tt><kbd>unzip student-files.zip</kbd> </p>
  </li>
  <li><strong>Test</strong> each method as soon as you finish writing it by issuing 
    the following command at the command prompt: 
    <p><tt>C:\&gt;</tt><kbd>java TestEmployeeArray</kbd> </p>

  </li>
  <li><strong>Implement</strong> the method <code>makeArray</code>.</li>
</ol>
<ul>
  <li><code><em>public static Employee[] makeArray(Employee first, Employee second, 
    Employee third)</em></code>. This method takes three <code>Employee</code> 
    objects and returns an <code>Employee</code> array with three elements. The 
    first element of the array contains a reference to the first argument; the 
    second element contains a reference to the second argument; and the third 
    element contains a reference to the third argument.</li>

</ul>
<blockquote> 
  <p>For example, consider the following objects:</p>
  <blockquote> 
    <pre>Employee[102,Mary Jones,60000.0]
Employee[101,Joe Smith,20000.0]
Employee[103,Richard Wong,40000.0]</pre>
  </blockquote>
  <p>If these objects are passed to <code>makeArray</code> in the indicated order, 
    <code>makeArray</code> will return the following array:</p>

  <blockquote> 
    <pre>{Employee[102,Mary Jones,60000.0],
 Employee[101,Joe Smith,20000.0],
 Employee[103,Richard Wong,40000.0]}</pre>
  </blockquote>
  <p>Note: <code>Employee[<em>ID</em>,<em>name</em>,<em>salary</em>]</code> is 
    the string representation of an <code>Employee</code> object. </p>

</blockquote>
<ol start="4">
  <li><strong>Implement</strong> the method <code>copyArray</code>. Use indexes to implement this method.</li>
</ol>
<ul>
  <li><code><em>public static Employee[] copyArray(Employee[] array)</em></code>. 
    This method takes an <code>Employee</code> array and returns a <em>new</em> 
    array with the same elements in the same order. </li>

</ul>
<blockquote> 
  <p>For example, consider the following array:</p>
  <blockquote> 
    <pre>{Employee[102,Mary Jones,60000.0],
 Employee[101,Joe Smith,20000.0],
 Employee[103,Richard Wong,40000.0]}</pre>
  </blockquote>
  <p>If <code>copyArray</code> is passed this array, it will return the following 
    array:</p>
</blockquote>

<ol start="5">
  <blockquote> 
    <pre>{Employee[102,Mary Jones,60000.0],
 Employee[101,Joe Smith,20000.0],
 Employee[103,Richard Wong,40000.0]}</pre>
  </blockquote>
  <li><strong>Implement</strong> the method <code>getEmployee</code>. Use a <code>for-each</code> loop to implement this method.</li>

</ol>
<ul>
  <li><code><em>public static Employee getEmployee(Employee[] array, int id)</em></code>. 
    This method takes two arguments, an <code>Employee</code> array and an employee