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<div align="center" class="title">JAVA程序員必讀：基礎篇（3）語言基礎</div>
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<div align="center"><font color="#666666">編譯：ZSC/太平洋網絡學院</font></div>
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<div align="right" class="gray"><a href="mailto:tntst@pconline.com.cn">［責編:爆破手］</a></div>
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<p class="article"> <b>語言基礎</b> </p>
<p></p>
<p class="article"><b>3.4.1 while和do-while語句</b></p>
<p class="article"> 你可以使用while語句當條件保持為true的時候，持續執行語句塊。While語句的通常語法為：
</p>
<p class="article">while (expression) {</p>
<p class="article"> statement</p>
<p class="article">}</p>
<p class="article"> 首先，while語句執行表達式，它將返回一個boolean數（true或者false）。如果表達式返回true，while語句執行相應的語句。While語句繼續測試表達式并執行塊代碼直到表達式返回false。</p>
<p class="article"> 下面給出一個例程WhileDemo，它使用while語句來瀏覽字符串的各個字符并復制字符串直到程序找到字符g為止：</p>
<p class="article">public class WhileDemo {</p>
<p class="article"> public static void main(String[] args) {</p>
<p></p>
<p class="article"> String copyFromMe = "Copy this string until you
" + </p>
<p> <span class="article">"encounter the letter 'g'.";</span></p>
<p class="article"> StringBuffer copyToMe = new StringBuffer();</p>
<p></p>
<p class="article"> int i = 0;</p>
<p class="article"> char c = copyFromMe.charAt(i);</p>
<p></p>
<p class="article"> while (c != 'g') {</p>
<p class="article"> copyToMe.append(c);</p>
<p class="article"> c = copyFromMe.charAt(++i);</p>
<p class="article"> }</p>
<p class="article"> System.out.println(copyToMe);</p>
<p class="article"> }</p>
<p class="article">}</p>
<p class="article"> 最后一行打印出來的數值為：Copy this strin. </p>
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