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 the <code class="clazz">super</code> keyword?</p>
    </div>
    <div class="ans">
        <ul><li><p>If a method overrides one of its superclass's methods, the overridden can be invoked through the use of the keyword <code class="clazz">super</code>.</p></li>
<li><p>The <code class="clazz">super</code> keyword can also be used to refer to a hidden field of the super type.</p></li>
<li><p>Interface default methods can be invoked using the <code class="clazz">super</code> keyword.</p></li>
<li><p>Constructors for superclasses can be invoked using the <code class="clazz">super</code> keyword.</p></li>
</ul>
<p>Pay attention to the code below for an instance of each of the above scenarios.</p>
<b>

```java
class ChildClass extends ParentClass implements AnInterface {

    int counter = 0;

    public ChildClass() {
        // invoking parent class's constructor
        // using the super keyword
        super(9);
    }

    public void accessHiddenFields() {
        // accessing parent class's counter field which gets
        // hidden with the local counter field.
        super.counter++;
        counter++;
        System.out.println("sublcass counter: " + counter + " parent class counter: " + super.counter);

        // accessing the interface's default method which is hidden
        AnInterface.super.accessHiddenFields();
    }
}



interface AnInterface {

    default void accessHiddenFields() {
        System.out.println("Default method of AnInterface invoked.");
    }
}

class ParentClass {

    protected int counter;

    public ParentClass(int val) {
        this.counter = val;
    }
}
```
</b>
</div>
</div>

<div>
   # Question # 1
    <div>
        <p>What is the <code>super</code> keyword?</p>
    </div>
    <div>
        <ul><li><p>If a method overrides one of its superclass's methods, the overridden can be invoked through the use of the keyword <code>super</code>.</p></li>
<li><p>The <code>super</code> keyword can also be used to refer to a hidden field of the super type.</p></li>
<li><p>Interface default methods can be invoked using the <code>super</code> keyword.</p></li>
<li><p>Constructors for superclasses can be invoked using the <code>super</code> keyword.</p></li>
</ul>
<p>Pay attention to the code below for an instance of each of the above scenarios.</p>
<b>

```java
class ChildClass extends ParentClass implements AnInterface {

    int counter = 0;

    public ChildClass() {
        // invoking parent class's constructor
        // using the super keyword
        super(9);
    }

    public void accessHiddenFields() {
        // accessing parent class's counter field which gets
        // hidden with the local counter field.
        super.counter++;
        counter++;
        System.out.println("sublcass counter: " + counter + " parent class counter: " + super.counter);

        // accessing the interface's default method which is hidden
        AnInterface.super.accessHiddenFields();
    }
}



interface AnInterface {

    default void accessHiddenFields() {
        System.out.println("Default method of AnInterface invoked.");
    }
}

class ParentClass {

    protected int counter;

    public ParentClass(int val) {
        this.counter = val;
    }
}
```
</b>
</div>
</div>

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

Super Keyword