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 annotations in Java and their utility?</p>
    </div>
    <div class="ans">
        <p><span class="hi-yl-b">Annotations, a form of metadata, provide data about a program that is not part of the program itself.</span> Annotations can be easily recognized in code because the annotation name is prefaced with the <code class="anno">@</code> character. Annotations have no direct effect on code operation, but at processing time, they can cause an annotation processor to generate files or provide informational messages. They are used for:</p>
<ul>
<li><p>Annotations can be used by the compiler to detect errors or suppress warnings</p></li>
<li><p>Software tools can process annotation information to generate code, XML files, and so forth.</p></li>
<li><p>Some annotations are available to be examined at runtime and allow runtime processing.</p></li>
</ul>
<p>Below is an example where a compiler is hinted to ignore warnings relating to unchecked generic operations using the annotation <code class="anno">@SuppressWarnings</code>. Annotations can be applied to declarations: declarations of classes, fields, methods, and other program elements.</p>
</div>
</div>

import java.util.List;
import java.util.ArrayList;

class Demonstration {
    
    // uncommenting the below line remove the
    // compile error
    //@SuppressWarnings("unchecked")    
    public static void main( String args[] ) {
        List companies = new ArrayList();
        companies.add("Educative.io");
        System.out.println(companies.get(0));
    }
}

<div class="card">
   # Question # 2
    <div class="qtn">
        <p>Give an example of creating a custom annotation</p>
    </div>
    <div class="ans">
        <p>The annotation type definition looks similar to an interface definition where the keyword interface is preceded by the <b><code class="anno">@</code></b> sign. Annotation types are a form of interface and contain <i>annotation type element</i> declarations, which look a lot like methods. Let's say we want to create an annotation that lets a user specify the longitude and latitude of the location at which he coded a class. The annotation would look like below:</p>
<b>

```java
// Creates an annotation which can be used to specify
// the longitude and latitude.
@Documented
@interface Location {

    // We provide a default value of 0
    double longitude() default 0;

    double latitude() default 0;
}

```
</b>
<p>The above annotation can be used as following</p>
<b>

```java
@Location(longitude = 37.400214, latitude = -121.943682)
public class MySuperClass {
    // Your awesome code here
}
```
</b>
<p>Note the use of the <code class="anno">@Documented</code> meta-annotation. Applying <code class="anno">@Documented</code> to <code class="anno">@Location</code> ensures that whichever class is annotated with <code class="anno">@Location</code> shows the <code class="anno">@Location</code> annotation in its Javadoc text.</p>

</div>
</div>

<div>
   # Question # 1
    <div>
        <p>What are annotations in Java and their utility?</p>
    </div>
    <div>
        <p><span>Annotations, a form of metadata, provide data about a program that is not part of the program itself.</span> Annotations can be easily recognized in code because the annotation name is prefaced with the <code>@</code> character. Annotations have no direct effect on code operation, but at processing time, they can cause an annotation processor to generate files or provide informational messages. They are used for:</p>
<ul>
<li><p>Annotations can be used by the compiler to detect errors or suppress warnings</p></li>
<li><p>Software tools can process annotation information to generate code, XML files, and so forth.</p></li>
<li><p>Some annotations are available to be examined at runtime and allow runtime processing.</p></li>
</ul>
<p>Below is an example where a compiler is hinted to ignore warnings relating to unchecked generic operations using the annotation <code>@SuppressWarnings</code>. Annotations can be applied to declarations: declarations of classes, fields, methods, and other program elements.</p>
</div>
</div>

<div>
   # Question # 2
    <div>
        <p>Give an example of creating a custom annotation</p>
    </div>
    <div>
        <p>The annotation type definition looks similar to an interface definition where the keyword interface is preceded by the <b><code>@</code></b> sign. Annotation types are a form of interface and contain <i>annotation type element</i> declarations, which look a lot like methods. Let's say we want to create an annotation that lets a user specify the longitude and latitude of the location at which he coded a class. The annotation would look like below:</p>
<b>

```java
// Creates an annotation which can be used to specify
// the longitude and latitude.
@Documented
@interface Location {

    // We provide a default value of 0
    double longitude() default 0;

    double latitude() default 0;
}

```
</b>
<p>The above annotation can be used as following</p>
<b>

```java
@Location(longitude = 37.400214, latitude = -121.943682)
public class MySuperClass {
    // Your awesome code here
}
```
</b>
<p>Note the use of the <code>@Documented</code> meta-annotation. Applying <code>@Documented</code> to <code>@Location</code> ensures that whichever class is annotated with <code>@Location</code> shows the <code>@Location</code> annotation in its Javadoc text.</p>

</div>
</div>

This lesson discusses annotations 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

Annotations

Question # 1