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<div align="center" class="title">JAVA程序員必讀：基礎篇（4）對象和簡單數據對象</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>對象和簡單數據對象</b></p>
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<p class="article"><b>（1）為什么有兩個String類：String 和StringBuffer</b></p>
<p class="article">JAVA平臺提供了兩個類：String和StringBuffer，它們可以儲存和操作字符串，即包含多個字符的字符數據。這個String類提供了數值不可改變的字符串。比如，如果你編寫一個方法，它需要字符串數據并且方法不能修改字符串，而要將一個String對象傳遞給方法。而這個StringBuffer類提供的字符串進行修改。當你直到字符數據要改變的時候你就可以使用StringBuffer。典型地，你可以使用StringBuffers來動態構造字符數據。比如，從一個文件讀文本數據。因為Strings是常量，所以它用起來比StringBuffers更有效，并且可以共享。因此在允許的情況下還是使用Strings。</p>
<p class="article"> 下面是一個例程StringsDemo，它反轉了字符串中的字符。這個程序同時使用了String和StringBuffer：</p>
<p class="article">public class StringsDemo {</p>
<p class="article"> public static void main(String[] args) {</p>
<p class="article"> String palindrome = "Dot saw I was Tod";</p>
<p class="article"> int len = palindrome.length();</p>
<p class="article"> StringBuffer dest = new StringBuffer(len);</p>
<p class="article"> for (int i = (len - 1); i >= 0; i--) {</p>
<p class="article"> dest.append(palindrome.charAt(i));</p>
<p class="article"> }</p>
<p class="article"> System.out.println(dest.toString());</p>
<p class="article"> }</p>
<p class="article">}</p>
<p class="article">這個程序的輸出為： </p>
<p class="article">doT saw I was toD</p>
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