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<div align="center" class="title">JAVA程序員必讀：基礎(chǔ)篇(5)---類和繼承</div>
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<div align="center"><font color="#666666">編譯：ZSC/太平洋網(wǎng)絡(luò)學(xué)院</font></div>
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<div align="right" class="gray"><a href="mailto:tntst@pconline.com.cn">［責(zé)編:爆破手］</a></div>
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<p class="article"><b><span class="article">5.1.6 </span></b><span class="article"><b>控制對(duì)類成員的訪問(wèn)</b></span><b>
</b></p>
<p> <b><span class="article">（</span></b><span class="article"><b>2）Protected</b></span></p>
<p class="article"> protected允許類本身、子類以及在相同包中的類訪問(wèn)這個(gè)成員。在允許類的子類訪問(wèn)而杜絕其它不相關(guān)的類的訪問(wèn)的時(shí)候，可以使用protected訪問(wèn)等級(jí)。Protected成員就象家庭秘密，家里人知道無(wú)所謂，但是就不讓外人知道，不是有“家臭不可外揚(yáng)”一說(shuō)嗎？，雖然這里不是什么“家臭”，但它是受protected的成員。</p>
<p class="article"> 為了聲明一個(gè)protected成員，使用關(guān)鍵字protected。首先，讓我們看看protected是怎樣影響在相同包內(nèi)的類的。假如上面的那個(gè)Alpha類現(xiàn)在被定義在一個(gè)（package）包Greek內(nèi)，它有一個(gè)protected成員變量和一個(gè)protected方法：
</p>
<p class="article">package Greek;</p>
<p class="article">public class Alpha {</p>
<p class="article"> protected int iamprotected;</p>
<p class="article"> protected void protectedMethod() {</p>
<p class="article"> System.out.println("protectedMethod");</p>
<p class="article"> }</p>
<p class="article">}</p>
<p class="article"> 現(xiàn)在，假設(shè)類Gamma也聲明為Greek包的一個(gè)成員（不是Alpha的子類）。Gamma類可以合法訪問(wèn)Alpha對(duì)象的iamprotected成員變量并且可以合法調(diào)用它的protectedMethod：
</p>
<p class="article">package Greek;</p>
<p class="article">class Gamma {</p>
<p class="article"> void accessMethod() {</p>
<p class="article"> Alpha a = new Alpha();</p>
<p class="article"> a.iamprotected = 10; // 合法</p>
<p class="article"> a.protectedMethod(); // 合法</p>
<p class="article"> }</p>
<p class="article">}</p>
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