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 is a class loader in Java?</p>
    </div>
    <div class="ans">
        <p><span class="hi-yl-b">A class loader is responsible for dynamically loading classes into the Java Virtual Machine.</span> Classes are loaded on demand in Java.</p>
</div>
</div>


<div class="card">
   # Question # 2
    <div class="qtn">
        <p>How many types of class loaders are there?</p>
    </div>
    <div class="ans">
        <p>There are three types of class loaders:</p>

<ul>
<li><p><b>Bootstrap Class Loader:</b> The bootstrap class loader loads the core Java libraries located in the <JAVA_HOME>/jre/lib directory. This class loader, which is part of the core JVM, is written in native code.</p></li>
<li><p><b>Extensions Class Loader:</b> The extensions class loader loads the code in the extensions directories (<JAVA_HOME>/jre/lib/ext, or any other directory specified by the <b><i>java.ext.dirs</i></b> system property. </p></li>
<li><p><b>System Class Loader:</b> The system class loader loads code found on <b><i>java.class.path</i></b>, which maps to the <b>CLASSPATH</b> environment variable.</p></li>
</ul>

<p>We can get the class loader for a class using <code class="mthd">getClassLoader()</code> method. An example appears below, run the code and examine the output.

</div>
</div>


import com.sun.javafx.util.Logging;

class Demonstration {
    public static void main( String args[] ) {
      
        System.out.println((new Demonstration()).getClass().getClassLoader());
     
        System.out.println(Logging.class.getClassLoader());
        
        System.out.println("".getClass().getClassLoader());
      
    }
}

<div class="ans">
<p>If you look at the output, you'll see that for the string object <code class="clazz">null</code> is output as the classloader. Some implementations return <code class="clazz">null</code> if the class is loaded by the bootstrap class loader, which is true for the string object.</p>
</div>

<div>
   # Question # 1
    <div>
        <p>What is a class loader in Java?</p>
    </div>
    <div>
        <p><span>A class loader is responsible for dynamically loading classes into the Java Virtual Machine.</span> Classes are loaded on demand in Java.</p>
</div>
</div>


<div>
   # Question # 2
    <div>
        <p>How many types of class loaders are there?</p>
    </div>
    <div>
        <p>There are three types of class loaders:</p>

<ul>
<li><p><b>Bootstrap Class Loader:</b> The bootstrap class loader loads the core Java libraries located in the <JAVA_HOME>/jre/lib directory. This class loader, which is part of the core JVM, is written in native code.</p></li>
<li><p><b>Extensions Class Loader:</b> The extensions class loader loads the code in the extensions directories (<JAVA_HOME>/jre/lib/ext, or any other directory specified by the <b><i>java.ext.dirs</i></b> system property. </p></li>
<li><p><b>System Class Loader:</b> The system class loader loads code found on <b><i>java.class.path</i></b>, which maps to the <b>CLASSPATH</b> environment variable.</p></li>
</ul>

<p>We can get the class loader for a class using <code>getClassLoader()</code> method. An example appears below, run the code and examine the output.

</div>
</div>


<div>
<p>If you look at the output, you'll see that for the string object <code>null</code> is output as the classloader. Some implementations return <code>null</code> if the class is loaded by the bootstrap class loader, which is true for the string object.</p>
</div>

This lesson introduces the concept of classloaders in Java.

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

Classloaders

Question # 1

Question # 2