【转载】Java进阶自测：面向对象基础知识掌握了吗？-子非愚，焉知愚之乐？

你是否已经参与过Java入门知识的自测？（点这里：Java编程基础自测题）

如果得分在80分以上，就来试试这个进阶版的自测吧，其中部分考题如下，答案附文后。（线上自测地址：【进阶版】Java面向对象编程基础自测题）

1. 现在有如下一段代码

<code class="language-java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Test</span> <span class="o">{</span> 
       <span class="kd">public</span> <span class="kt">int</span> <span class="nf">aMethod</span><span class="o">()</span> <span class="o">{</span>
              <span class="kd">static</span> <span class="kt">int</span> <span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="o">;</span>
              <span class="n">i</span><span class="o">++;</span>
              <span class="k">return</span> <span class="n">i</span><span class="o">;</span>
       <span class="o">}</span>
       <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span> <span class="n">args</span><span class="o">[])</span> <span class="o">{</span>
              <span class="n">Test</span> <span class="n">test</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Test</span><span class="o">();</span>
              <span class="n">test</span><span class="o">.</span><span class="na">aMethod</span><span class="o">();</span>
              <span class="kt">int</span> <span class="n">j</span> <span class="o">=</span> <span class="n">test</span><span class="o">.</span><span class="na">aMethod</span><span class="o">();</span>
              <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">j</span><span class="o">);</span>
       <span class="o">}</span>
<span class="o">}</span>
</code>

将产生哪种结果：

A. Compilation will fail

B. Compilation will succeed and the program will print“0”

C. Compilation will succeed and the program will print“1”

D. Compilation will succeed and the program will print“2”

2. 如要在字符串s（内容为“welcome to mldn !! ”），中，发现字符’t’的位置，应该使用下面哪种方法？

A. mid(2,s);

B. charAt(2);

C. s.indexOf(‘t’);

D. indexOf(s,’v’);

3. 编译和运行下面代码可能会发生什么？

<code class="language-java"><span class="kd">class</span> <span class="nc">Base</span> <span class="o">{</span>
    <span class="kd">private</span> <span class="kt">void</span> <span class="nf">amethod</span><span class="o">(</span><span class="kt">int</span> <span class="n">iBase</span><span class="o">)</span> <span class="o">{</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Base.amethod"</span><span class="o">);</span>
    <span class="o">}</span>
<span class="o">}</span>    
<span class="kd">class</span> <span class="nc">Over</span> <span class="kd">extends</span> <span class="n">Base</span> <span class="o">{</span>
    <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span> <span class="n">args</span><span class="o">[])</span> <span class="o">{</span>
        <span class="n">Over</span> <span class="n">o</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Over</span><span class="o">();</span>
        <span class="kt">int</span> <span class="n">iBase</span> <span class="o">=</span> <span class="mi">0</span> <span class="o">;</span>
         <span class="n">o</span><span class="o">.</span><span class="na">amethod</span><span class="o">(</span><span class="n">iBase</span><span class="o">)</span> <span class="o">;</span>
    <span class="o">}</span>
    <span class="kd">public</span> <span class="kt">void</span> <span class="nf">amethod</span><span class="o">(</span><span class="kt">int</span> <span class="n">iOver</span><span class="o">)</span> <span class="o">{</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Over.amethod"</span><span class="o">);</span>
    <span class="o">}</span>
<span class="o">}</span>
</code>

A. Compile time error complaining that Base.amethod is private

B. Runntime error complaining that Base.amethod is private

C. Output of Base amethod

D. Output of Over.amethod

4. 现在有如下一段程序

<code class="language-java"><span class="kd">class</span> <span class="nc">super</span> <span class="o">{</span>
    <span class="n">String</span> <span class="n">name</span> <span class="o">;</span>
    <span class="kd">public</span> <span class="nf">super</span><span class="o">(</span><span class="n">String</span> <span class="n">name</span><span class="o">)</span> <span class="o">{</span>    
        <span class="k">this</span><span class="o">.</span><span class="na">name</span> <span class="o">=</span> <span class="n">name</span> <span class="o">;</span>
    <span class="o">}</span>
    <span class="kd">public</span> <span class="kt">void</span> <span class="nf">fun1</span><span class="o">()</span>     <span class="o">{</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"this is class super !"</span><span class="o">+</span><span class="n">name</span><span class="o">);</span>
    <span class="o">}</span>
<span class="o">}</span>
<span class="kd">class</span> <span class="nc">sub</span> <span class="kd">extends</span> <span class="kd">super</span> <span class="o">{</span>
    <span class="kd">public</span> <span class="kt">void</span> <span class="nf">fun1</span><span class="o">()</span>     <span class="o">{</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"this is class sub !"</span><span class="o">+</span><span class="n">name</span><span class="o">);</span>
    <span class="o">}</span>
<span class="o">}</span>
<span class="kd">class</span> <span class="nc">Test</span> <span class="o">{</span>
    <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span> <span class="n">args</span><span class="o">[])</span> <span class="o">{</span>
        <span class="kd">super</span> <span class="n">s</span> <span class="o">=</span> <span class="k">new</span> <span class="n">sub</span><span class="o">();</span>
    <span class="o">}</span>
<span class="o">}</span>
</code>

运行上面的程序可能会出现的结果？

A. this is class super !

B. this is class sub !

C. 编译时出错

D. 运行时出错

5. 现在有如下一段程序

<code class="language-java"><span class="kd">class</span> <span class="nc">Happy</span> <span class="o">{</span>
    <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span> <span class="n">args</span><span class="o">[])</span> <span class="o">{</span>
        <span class="kt">float</span> <span class="o">[][]</span> <span class="n">f1</span> <span class="o">=</span> <span class="o">{{</span><span class="mf">1.2f</span><span class="o">,</span><span class="mf">2.3f</span><span class="o">},{</span><span class="mf">4.5f</span><span class="o">,</span><span class="mf">5.6f</span><span class="o">}}</span> <span class="o">;</span>
        <span class="n">Object</span> <span class="n">oo</span> <span class="o">=</span> <span class="n">f1</span> <span class="o">;</span>
        <span class="n">f1</span><span class="o">[</span><span class="mi">1</span><span class="o">]</span> <span class="o">=</span> <span class="n">oo</span> <span class="o">;</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Best Wishes "</span><span class="o">+</span><span class="n">f1</span><span class="o">[</span><span class="mi">1</span><span class="o">]);</span>
    <span class="o">}</span>
<span class="o">}</span>
</code>

该程序会出现何种效果？

A. {4.5,5.6}

B. 4.5

C. compilation error in line NO.5

D. exception

6. 在一个类文件中，导入包、类和打包是怎样的排列顺序？

A. package、import、class；

B. class、import、package

C. import、package、class

D. package、class、import

7. 如果你试图编译并运行下列代码时可能会打印输出什么？

<code class="language-java"><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">9</span> <span class="o">;</span>
<span class="k">switch</span><span class="o">(</span><span class="n">i</span><span class="o">)</span> <span class="o">{</span>
    <span class="k">default</span><span class="o">:</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"default"</span><span class="o">);</span>
    <span class="k">case</span> <span class="mi">0</span> <span class="o">:</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"zero"</span><span class="o">);</span>
        <span class="k">break</span> <span class="o">;</span>
    <span class="k">case</span> <span class="mi">1</span> <span class="o">:</span> <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"one"</span><span class="o">);</span>
    <span class="k">case</span> <span class="mi">2</span> <span class="o">:</span> <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"two"</span><span class="o">);</span>
<span class="o">}</span>
</code>

A. default

B. default , zero

C. error default clause not defined

D. no output displayed

8. 当你编译下列代码可能会输出什么？

<code class="language-java"><span class="kd">class</span> <span class="nc">Test</span> <span class="o">{</span>
    <span class="kd">static</span> <span class="kt">int</span> <span class="n">i</span> <span class="o">;</span>
    <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span> <span class="n">args</span><span class="o">[])</span> <span class="o">{</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">i</span><span class="o">);</span>
<span class="o">}</span>
<span class="o">}</span>
</code>

A. Error Variable i may not have been initialized

B. null

C. 1

D. 0

9. 下面代码会存在什么问题？

<code class="language-java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">MyClass</span> <span class="o">{</span>
    <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span> <span class="n">arguments</span><span class="o">[])</span>     <span class="o">{</span>
        <span class="n">amethod</span><span class="o">(</span><span class="n">arguments</span><span class="o">);</span>
    <span class="o">}</span>
    <span class="kd">public</span> <span class="kt">void</span> <span class="nf">amethod</span><span class="o">(</span><span class="n">String</span><span class="o">[]</span> <span class="n">arguments</span><span class="o">){</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">arguments</span><span class="o">);</span>
        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">arguments</span><span class="o">[</span><span class="mi">1</span><span class="o">]);</span>
    <span class="o">}</span>
<span class="o">}</span>
</code>

A. 错误，void amethod()不是static类型

B. 错误，main()方法不正确

C. 错误，数组必须导入参数

D. 方法amethod()必须用String类型描述

10. 为Demo类的一个无形式参数无返回值的方法method书写方法头，使得使用类名Demo作为前缀就可以调用它，该方法头的形式为？

A. static void method( )

B. public void method( )

C. final void method( )

D. abstract void method( )

答案：ACDCC ABDAA 你答对了几道题呢？

更多学习资源，敬请关注：阿里云大学 – 知乎专栏

【转载】Java进阶自测：面向对象基础知识掌握了吗？

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