Write better code

Java Code Checker

Check your Java code security before your next PR commit and get alerts of critical bugs using our free online Java code checker — powered by Snyk Code.

Sign up for free to unlock the the full power of Snyk, no credit card required.


How to use the free code checker


Copy and paste your Java code into the editor.


Select your language from the dropdown.


Click the Check code button.


Use the results to improve your Java code.

Get code security right from your IDE

This free code checker can find critical vulnerabilities and security issues with a click. To take your application security to the next level, we recommend using Snyk Code for free right from your IDE.


  • File I/O corruptions

  • API contract violations

  • Null dereferences

  • Process/threading deadlock problems

  • Incorrect type checking

  • Expression logic mistakes

  • Regular expression denial of service

  • Invalid time/date formatting

  • Resource leaks


  • Missing input data sanitization

  • Insecure password handling

  • Protocol insecurities

  • Indefensive permissions

  • Man-in-the-Middle attacks

  • Weak cryptography algorithms

  • Information disclosure

  • Code injection

  • SQL injection

Java code security powered by Snyk Code

This free web based Java code checker is powered by Snyk Code. Sign up now to get access to all the features including vulnerability alerts, real time scan results, and actionable fix advice within your IDE.

Human-in-the-Loop JavaScript Code Checker

Snyk Code is an expert-curated, AI-powered JavaScript code checker that analyzes your code for security issues, providing actionable advice directly from your IDE to help you fix vulnerabilities quickly.


Scan and fix source code in minutes.


Fix vulns with dev friendly remediation.

Integrated in IDE

Find vulns early to save time & money.


Integrates into existing workflow.

More than syntax errors

Comprehensive semantic analysis.

AI powered by people

Modern ML directed by security experts.

In-workflow testing

Automatically scan every PR and repo.

CI/CD security gate

Integrate scans into the build process.

Frequently asked questions

What is Java code security?

Java, as a programming language, has a number of inherent features that make it secure. The platform itself includes security measures such as strong data typing, automatic memory management, bytecode verification, and secure class loading. These inherent platform features make Java relatively secure by default.

In addition, developers can opt to add additional controls like cryptography, authentication, authorization, Public Key Infrastructure (PKI), secure communication, and XML signatures. While all of these security controls are readily available to add to your Java program, you must know to include them in the first place; they are not automatically enabled.

While Java’s built-in security measures are robust, it still has gaps that must be addressed by your teams. For instance, using a framework to build your Java application introduces the possibility of new vulnerabilities. Dependencies within your application also open up your software to possible risks. Because of this, your team needs to be aware of which dependencies your software includes, and whether or not they are secure. A tool like Snyk Open Source can uncover which dependencies are interconnected with your application, enabling your team to remediate or replace insecure components.

What is Java code quality?

Java programs should be written to be clean and straightforward. Clean, quality code means that:

  • The order of execution, from beginning to end, makes sense logically and structurally

  • It’s easy to understand how the different parts of code interact and work together

  • Each class, function, method, and variable has a clear role. They are all clearly named.

  • Classes and methods only fulfill one task and work as expected

When your code is built cleanly from the start, it’s easier to read, less prone to errors, and, by default, more secure. A few other ways to build high-quality Java code include avoiding hardcoding, maintaining thorough logs, turning repetitive code into a separate class or method, and only using a few parameters for each method.

The key to good quality Java code: Write it so that when someone else opens your project, they can see the documentation, and as a result, understand how it all works.

How to use a Java code checker to improve code quality and security practices

Creating high-quality, secure code is easier said than done. Using an automated code checker is the best way to improve code quality and security practices.

A code checker analyzes your code, checking its syntax, style, and documentation completeness. A security-focused code checker will also check system configuration, data flow, semantics, and structure for possible security issues. Because of this, many organizations use code checkers to perform static application security testing (SAST).

A Java code checker should be able to do the following:

  • Integrate into your developers’ existing processes

  • Seldom return false positives or negatives

  • Flag the issues by specific line

  • Scan source code at every stage of development (a DevSecOps approach)

  • Combine with other code quality tools, such as linters

  • Reference a comprehensive database of vulnerabilities

  • Go beyond flagging quality or security flaws by also giving actionable suggestions on

     how to fix them

Why is a Java code checker vital to secure development?

Secure development requires a security-from-the-start mindset. Security measures need to be added into the very beginning stages of your development lifecycle, all the way up until production. Waiting until the end of the cycle to remediate security issues will cause your developers to backtrack and examine code that was written weeks, or even months ago to identify and fix what went wrong. It will end up costing far more than remediating these issues earlier in the process.

Instead, a Java code checker enables developers to create a secure software development lifecycle (SDLC) by giving them the ability to automatically scan code in small batches, just minutes after it’s written. Code checkers integrate well into other automated processes, such as CI/CD pipelines, and help teams to ensure that their code is clean, easily readable, and free of bugs and security errors.

What is a syntax error in Java?

A syntax error occurs when a Java parser cannot comprehend the command you are trying to execute because your code does not adhere to the programming language’s rules. Because Java is a compiled programming language, this error prevents the code from being compiled and therefore, keeps it from running. Often, this is caused by a misspelling, a missing punctuation mark, or an undefined variable.

Common Java syntax and logical errors

There are a few common syntax and logic errors that your Java code checker will find. Regardless of how experienced your developers are, they still might fall into some of these common syntax issues, simply because they’re human and these mistakes are easy to make. Here are a few common errors:

  • Using a variable, but failing to define it or misspelling it

  • Missing a symbol such as a semicolon, quotation mark, or parentheses

  • Attempting to assign values to incompatible variables (i.e. assigning a decimal value when the variable can only process integers)

  • Trying to use a type that does not exist, is misspelled, or cannot be easily located by the program.

What are the benefits of an AI-powered Java code checker

An AI-powered Java code checker catches errors and vulnerabilities more quickly and accurately than manual checks such as peer code reviews or pair programming. To facilitate artificial intelligence, the code checker is trained by hundreds of thousands of open source projects. In other words, an AI-powered code checker can comprehend what’s “normal” for Java programming and use this knowledge to find quality and security errors, then provide intelligent suggestions for remediation. As a result, developers can find and remediate code errors, intelligently and automatically. Snyk code is one of the fastest solutions for checking your code, and enables fast feedback cycles and iterations for continuous improvement. It can also help your developers learn more about security as they code, with fix suggestions and explainers.

Check your Java code, right within your existing workflows.

Secure your Java code as you develop. Snyk’s free IDE pluginsincluding Intellijscan your Java code for risk and quality errors, then provide actionable insights to help you fix them.

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Snyk is a developer security platform. Integrating directly into development tools, workflows, and automation pipelines, Snyk makes it easy for teams to find, prioritize, and fix security vulnerabilities in code, dependencies, containers, and infrastructure as code. Supported by industry-leading application and security intelligence, Snyk puts security expertise in any developer’s toolkit.

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