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>Can lambda be thought of as  replacement of anonymous classes for implementing functional interfaces?</p>
    </div>
    <div class="ans">
        <p>No, one primary difference between the two is that the <span class="hi-yl-b">anonymous classes can maintain state as they can have instance or static variables whereas lambda expressions are just method implementations.</span></p>
</div>
</div>

<div class="card">
   # Question # 2
    <div class="qtn">
        <p>In the below example, why do we not need to specify the type of the parameters being passed in to the lambda expression?</p>
<b>

```java
interface CrunchNumbers {

    void work(int a, int b);

}

void test() {

    // k and j don't have their types defined.
    myMethod((k, j) -> {
        System.out.println(k % j == 0 ? "exactly divisible" : "not divisible");
    });

}
```
</b>
</div>
    <div class="ans">
        <p>We can skip specifying the types of the variables being passed into the method being implemented by the lambda expression because the compiler is intelligent enough to infer the types looking at the interface definition. This is called <span class="hi-yl">type inference</span>. The compiler infers the type of a parameter by looking elsewhere for the type - which is the interface's function definition. <span class="hi-yl-b">More generally, the process of automatically deducing unspecified data types of an expression based on the contextual information is called type inference.</span></p>
<p>Specifying parameter types for a lambda expression may sometimes be necessary if the compiler cannot infer the parameter types from the functional interface method the lambda is matching.</p>
<p>If the data types are specified, the code still works correctly as shown below.</p>
</div>
</div>

<div>
   # Question # 1
    <div>
        <p>Can lambda be thought of as  replacement of anonymous classes for implementing functional interfaces?</p>
    </div>
    <div>
        <p>No, one primary difference between the two is that the <span>anonymous classes can maintain state as they can have instance or static variables whereas lambda expressions are just method implementations.</span></p>
</div>
</div>

<div>
   # Question # 2
    <div>
        <p>In the below example, why do we not need to specify the type of the parameters being passed in to the lambda expression?</p>
<b>

```java
interface CrunchNumbers {

    void work(int a, int b);

}

void test() {

    // k and j don't have their types defined.
    myMethod((k, j) -> {
        System.out.println(k % j == 0 ? "exactly divisible" : "not divisible");
    });

}
```
</b>
</div>
    <div>
        <p>We can skip specifying the types of the variables being passed into the method being implemented by the lambda expression because the compiler is intelligent enough to infer the types looking at the interface definition. This is called <span>type inference</span>. The compiler infers the type of a parameter by looking elsewhere for the type - which is the interface's function definition. <span>More generally, the process of automatically deducing unspecified data types of an expression based on the contextual information is called type inference.</span></p>
<p>Specifying parameter types for a lambda expression may sometimes be necessary if the compiler cannot infer the parameter types from the functional interface method the lambda is matching.</p>
<p>If the data types are specified, the code still works correctly as shown below.</p>
</div>
</div>

This lesson continues discussion on lambdas 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

More on Lambdas

Question # 1

Question # 2