FullStack Labs

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Hire our Elite Java Developers

FullStack Labs is a leading team of Java developers, engineers, programmers, coders, and architects. Uber, Siemens, and hundreds of other companies have chosen us for their mission-critical Java development projects.

Hire Our Elite java Developers Now
What's included

We’ll review your code base and provide a report that includes quality scores for the following:

  • Test suite and test coverage
  • Code quality, including a CodeClimate report
  • How soon can FullStack start on my project?
  • Dependencies
  • Error and performance monitoring
  • Documentation
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Trusted By:
UberSiemensEricssonNFIBEkso BionicsCalifornia

Some of our expert Java developers.

By combining USA and Canada technical leads and project managers with Senior Developers in Latin America, we offer clients the quality, security, and convenience of onshore development paired with the cost savings of nearshore development.
Roberto Sawamura
Senior Software Engineer
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Latin America
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 Years of Experience

Senior Software Engineer, Roberto Sawamura, Latin America

Mariano Dilascio
Senior Software Engineer
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Latin America
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 Years of Experience

Senior Software Engineer, Mariano Dilascio, Latin America

Leandro Sinhorini
Senior Software Engineer
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Latin America
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 Years of Experience

Senior Software Engineer, Leandro Sinhorini, Latin America

Dionis Vega
Senior Database Administrator
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Latin America
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 Years of Experience

Shawn Cheng
Software Architect
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 Years of Experience

FullStack Labs, Senior Software Engineer‍

Sabrina Sergio
Senior Software Engineer
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Latin America
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 Years of Experience

Mid-Level Software Engineer, Sabrina Sergio, Latin America

Client Testimonials

We really appreciate FullStack’s expertise, and understanding of best practices, for React.js. Their team really is working at the bleeding edge of the technology. After implementing their recommendations we’ve been able to increase automation and decrease labor by 50% in our AR department, freeing up our people for more productive uses.

It’s not easy to get 5 stars from me but you guys have been great! You show up on time, you finish within the schedule. We’re doing accounting and financial systems which means that you have to learn the business side of it. It’s not only software, you have to understand the workflow. Our experience has been amazing.

- George Grant -
Director of IT, The Coding Network

Working with FullStack Labs (Gisselle and Charly) has been one of, if not THE, best work experiences I’ve had in my life - and I’ve built a lot of stuff in my 70+ years.

- Bill Estberg -
President, chill-n-go

How to Hire Java developers Through FullStack Labs

  • 1. Talk to us!

    We will work with you to understand your technical need, team dynamics, and goals.

  • 2. Meet our Available Talent

    We’ll send you FullStack Java developers that match your technical requirements, with links to their FullStack profile page which outlines their work experience and technical abilities, as well as their FullStack technical summary page, which includes a 60 minute video of the developer completing FullStack’s coding challenge, and a plethora of other technical information from their interview with us.

  • 3. 14 Day Risk-free Trial

    Start the engagement. Work with your new Java developer for a trial period, ensuring they're the right fit."

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Engagement Models for Java Projects

New Java Apps

We design and build greenfield apps of all shapes and sizes using Java combined with a React.js, Ember.js or Angular.js javascript frameworks.

Existing Java Apps

Have a legacy Java app? We’re here to help. From debugging and maintenance to feature development and DevOps, we'll tailor a development plan to meet your needs.

Java Team Augmentation

Need to add a Java developer to your existing team? We'll seamlessly integrate as many developers as needed, to help you go faster and level up your team's skills.

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FullStack Labs is proudly remote.

We have an ever growing team of incredible people currently located in these countries.
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Meet our Leadership Team

Our Clients Love Us, And You Will Too.

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Let's Talk!

We’d love to learn more about your project.
Engagements start at $75,000.

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Essential Technical Java Interview Questions

FullStack Labs is a leading team of Java developers, engineers, programmers, coders, and architects. Uber, Siemens, and hundreds of other companies have chosen us for their mission-critical software development projects. Java is a crucial tool to develop your project, here are a few Java Interview Questions you can use to screen your Java candidates:

Q: What is the difference between access modifiers and when would you use each?


  • Private - used for members that can only be modified/accessed by members of the same class.  Can be used to protect against changes from outside classes which use the class.
  • Protected - used for members that can only be modified/accessed by members of the same class or those that extend the class.  Can be useful for access to a member when using abstract classes or classes whose functionality can be or are intended to be extended upon.
  • Public - used for members that can be accessed from anywhere.  Used for methods and variables that can be accessed/called by any method which makes use of that class.  These generally define the functionality the class ""delivers"" for outside members.
  • Default (bonus) - when no access modifier is used the access defaults to this.  The members can only be accessed in the same package.  Can be used by members that are only intended to be modified by members in the same package (less likely to be used).

Note: There are probably more details/examples they can go into in regards to access modifiers.

Q: Explain what/when an abstract class and interface would be used


  • Abstract - defines a common implementation of methods and variables that can be extended by other classes. Most commonly used to define classes that share common logic.  A class can only extend one class.
  • Interface - defines common variables and methods whose implementation must be defined by the classes which implement them.  Most commonly used to define classes that have functionality in common but whose internal implementation of that functionality differs.  A class can implement multiple interfaces.

Note: There are probably more details/examples they can go into in regards to abstract/implementation.

Q: How arguments are passed in Java?


If the original variable type is primitive (int,string, ...), then a copy of the variable is created inside the stack and then is passed to the method.

If the variable type is not primitive (Objects, ...), then a new pointer is created inside the stack which points to the actual object, and a new reference is passed to the method (Two references are pointing to the same object)

Q: What is the Java Reflection?


This is a feature that allows read and manipulate internal properties for our classes, objects, etc.

For example, it's possible for a Java class to obtain the names of all its methods and display them to the users automatically.

Q: How can you define Java Stream API?


Streams are wrappers around data where you can operate, execute different functions very similar to functional programming making bulk processing (calculation, transformation) to your data source.

Note: Do not confuse with Java I/O stream. A good comparison would be processing data like JS arrays with functions like (.map.filter.reduce, ...etc).

Q: What is the difference between a Set, a List, and a Map?


A Set is an interface that defines a collection that does not allow repetitions. The elements in a Set cannot be accessed by the index. Some implementations of Set are HashSet, LinkedHashSet, and TreeSet.

A List is an interface that defines a collection that guarantees the order of insertion, allows the elements to be gotten by their index, and may allow repetitions. Some implementations of List are ArrayList, Stack, and LinkedList.

A Map is an interface that defines a data structure that has a key and value relationship, elements inserted as keys cannot be repeated, and the value elements can be accessed by their keys. Values can be repeated. Some classes which implement Map are TreeMap, LinkedHashMap, and HashMap.

Q: What is a default method?


The default method was introduced in Java 8. It allows interfaces to have a default implementation of the methods they define. If the default method is not overridden by the class which implements the interface, the interface’s implementation will be used, as occurs using inheritance.

Q: What is an anonymous Class?


An anonymous Class is a local class implementation of an Interface. You can use it when you have a specific purpose for the implementation inside a method, like an event handling for example. The code below shows it:

 Button submit = new Button(""Submit"");
 submit.setOnAction(new EventHandler<ActionEvent>() {
    public void handle(ActionEvent e) {
            //execute some action when the button is clicked

The class Button has a method called setOnAction, which must receive an implementation of the Interface EventHandler as a parameter. This interface defines a method called
handle. To avoid creating another class that will have this implementation, it is possible to create a local implementation-specific for this action of this button called Submit. This code cannot be reused.

Note: Anonymous classes can be used for any Interface, it is not a specific feature for event handling.