The ultimate guide to Java interviews with 300+ real-world questions and answers. Get interview-ready in just a few hours with strategies developed by FAANG engineers.

It’s very common to have interviews testing your knowledge of a programming language you claim to be an expert in.

If you've got an interview coming up on Java soon and need to get up to speed, this is the ideal course for you. You'll refresh your memory on everything from the basics to more advanced functionality you’re likely to be asked about. Even if you're using Java every day, you may not have been exposed to parts of it in some time, so it's always useful to make sure you're updated.

This course features more than 300 of the most commonly asked core Java interview questions that you're likely to face as an experienced software engineer. You'll get to explore questions by topic, as well as see detailed answers for each one, and plenty of live code examples where relevant. Get started today.

The Java Interview Handbook: 300+ Interview Questions

<div class="card">
   # Question # 1
    <div class="qtn">
    <p>What are some of the steps you’ll take to improve the memory footprint of a Java application?</p>
    </div>
    <div class="ans">
        <ul>
<li><p>Limiting the scope of local variables. Each time the top scope from the stack is popped up, the references from that scope are lost, and this could make objects eligible for garbage collection.</p></li>
<li><p>Explicitly set variable references to <code class="clazz">null</code> when not needed. This will make objects eligible for garbage collection.</p></li>
<li><p>Avoid finalizers. They slow down program performance and do not guarantee anything.</p></li>
<li><p>Do not use strong references where weak or soft references apply. The most common memory pitfalls are caching scenarios, when data is held in memory even if it might not be needed.</p></li>
<li><p>JVM can be configured based on application requirements. There are a number of knobs that one can use to tune and tweak the memory performance. For instance:</p>

<ul>
<li><p><code class="mthd">-Xms</code> specifies the initial heap size</p></li>
<li><p><code class="mthd">-Xmx</code> specifies the maximum heap size</p></li>
<li><p><code class="mthd">-Xss</code>specifies the thread stack size</p></li>
<li><p><code class="mthd">-Xmn</code> specifies the young generation size</p></li>
</ul>
</li>
<li><p>The JVM can be instructed to dump the heap on an <code class="mthd">OutOfMemoryError</code> exception by adding the <code class="mthd">-XX:+HeapDumpOnOutOfMemoryError</code> argument to the JVM. The heap can then be visualized for memory leaks and consumption using tools such as eclipse's MAT,
jvisualvm or yourkit profiler.</p></li>
<li><p>The <code class="mthd">-verbose:gc</code> option can be used to get garbage collector's output.</p></li>
</ul>
</div>
</div>


<div>
   # Question # 1
    <div>
    <p>What are some of the steps you’ll take to improve the memory footprint of a Java application?</p>
    </div>
    <div>
        <ul>
<li><p>Limiting the scope of local variables. Each time the top scope from the stack is popped up, the references from that scope are lost, and this could make objects eligible for garbage collection.</p></li>
<li><p>Explicitly set variable references to <code>null</code> when not needed. This will make objects eligible for garbage collection.</p></li>
<li><p>Avoid finalizers. They slow down program performance and do not guarantee anything.</p></li>
<li><p>Do not use strong references where weak or soft references apply. The most common memory pitfalls are caching scenarios, when data is held in memory even if it might not be needed.</p></li>
<li><p>JVM can be configured based on application requirements. There are a number of knobs that one can use to tune and tweak the memory performance. For instance:</p>

<ul>
<li><p><code>-Xms</code> specifies the initial heap size</p></li>
<li><p><code>-Xmx</code> specifies the maximum heap size</p></li>
<li><p><code>-Xss</code>specifies the thread stack size</p></li>
<li><p><code>-Xmn</code> specifies the young generation size</p></li>
</ul>
</li>
<li><p>The JVM can be instructed to dump the heap on an <code>OutOfMemoryError</code> exception by adding the <code>-XX:+HeapDumpOnOutOfMemoryError</code> argument to the JVM. The heap can then be visualized for memory leaks and consumption using tools such as eclipse's MAT,
jvisualvm or yourkit profiler.</p></li>
<li><p>The <code>-verbose:gc</code> option can be used to get garbage collector's output.</p></li>
</ul>
</div>
</div>


This lesson talks about the common memory issues faced when running Java programs.

Java Ecosystem

Methods

Classes

Interfaces

Inheritance

Lambda Expressions

Generics

Multi-Threading

Memory Management

Collections

Exceptions

Reflection

Serialization

Miscellaneous Topics

Java in Practice

Patterns

The End

Memory Tuning

Question # 1