Fix the 5 Most Common Types of Runtime Errors in Java

As the name suggests, runtime errors occur during the execution of a software program. They occur when an application is running. Whenever an application behaves in a way that deviates negatively from its established requirements, it means that a runtime error has occurred.

Such a broad definition isn’t very useful when Java runtime errors stop your application in its tracks. Let’s take a closer look at the five most common runtime errors encountered by Java programmers, along with the steps and strategies for resolving them.

Top 5 Runtime Errors in Java

The most common runtime errors in Java can be broken down into the following five categories:

  1. Data entry errors
  2. Insufficient enforcement resources
  3. Poorly implemented logic
  4. Changes to external resources
  5. Third-party vulnerabilities

Entry cleanup failures

There are countless ways user input can corrupt an application.

On an HTML comment board, a user allowed to innocently submit an unencrypted message less than (bigger than sign (>) has the potential to completely ruin the rendering ability of this web page. Similarly, word processors designed to expect all ASCII-formatted input may terminate prematurely if they receive emojis or non-standard character input.

Data cleansing provides these benefits to organizations.

Even more nefarious, one of hackers’ favorite attack vectors is SQL injection, which hides a malicious executable database query in an otherwise harmless input field. This can not only cause an application to fail, but also relinquish control of the entire data layer.

The entrance disinfection process, or data cleaning, converts the wide range of data likely to be entered into applications into a safe range of values ​​that a program understands. Using these libraries helps mitigate runtime errors caused by entry cleanup failures.

Popular Java frameworks such as Apache BVal and Hibernate Validator perform simple annotation-based input cleanup and integrate easily into any Java-based application.

Insufficient enforcement resources

Software developers are not responsible for every type of runtime error that occurs. Many runtime errors in Java involve resource limitations caused by issues with the underlying infrastructure. Examples include: network timeouts, low memory conditions, CPU overuse, or inability to schedule a thread on the CPU.

One way to avoid resource-related runtime errors is to use a load testing tool, such as JMeter or LoadRunner, in an application’s CI/CD pipeline. If these tools detect a potential performance issue, they can terminate the application before it progresses through the pipeline to production deployment.

The load of some applications varies considerably. For example, a financial services application may show a constant load most of the time, but be extremely busy at the end of the trading day. A tax service may reach a peak load before the filing deadline but have relatively low load the rest of the year.

DevOps teams should monitor their performance metrics with tools to preemptively detect and mitigate resource-related runtime errors. Examples of such tools include JDK Flight Recorder and Java Mission Control.

For applications with completely unpredictable workloads, use cloud-based load balancing technology to elastically allocate resources. This eliminates both under-allocated resources and the trap of purchasing expensive, infrequently used hardware.

Poorly implemented logic

Just because the code compiles doesn’t mean it works correctly. Code often contains logical issues that cause an application to fail at runtime.

Java contains a built-in construct to handle a class of common code-related runtime errors called RuntimeException, or the unchecked exception. Java 17 sets 78 such errors in the SDK alone, and other projects and frameworks additionally set their own RuntimeException errors.

The most common RuntimeExceptions encountered in Java include:

  • ArithmeticException, for divide-by-zero errors;
  • ClassCastException, for data type conversion errors;
  • ConcurrentModificationException, for incorrectly implemented parallel computations;
  • IndexOutOfBoundsException, when a nonexistent element in an array is accessed; and
  • NullPointerException, when a method is called on a null object.

Developers are not required to handle unchecked exceptions in their code. But an unchecked exception that is thrown and ignored will terminate an application.

At the very least, every app should include a generic exception harness that can catch every possible RuntimeException, log the error, and allow the problematic thread of execution to die rather than abort the whole app.

Configuring external resources

Enterprise applications rarely exist in an isolated bubble. They typically interact with everything from NoSQL databases and relational systems to Kafka queues and RESTful APIs. Unfortunately, if your application fails to connect to a required external system, it inevitably results in a runtime error.

An external resource may precipitate a runtime error if one of the following occurs without a corresponding update to the calling program:

  • an IP address changes;
  • changing credentials;
  • modification of the firewall configuration; Where
  • the external system goes down for maintenance.

Applications need to react quickly when resources change. The 12-Factor app insists that developers keep all configuration data external to the app so apps can react quickly when resources change. The ability to update properties files without modifying the code base allows applications to handle changes from external resources and avoids an application rebuild.

In a related way, chaos engineering tools randomly terminate processes that an application depends on. Such tools force developers to write code that remains responsive and resilient even when external systems fail.

The inherent problem with external resources is that developers cannot control them, but they can control how an application responds when these external resources fail. Anticipate run-time errors generated by systems you don’t control and write applications that respond correctly when these external systems fail.

Third-party library vulnerabilities

Any non-trivial enterprise application includes dozens of dependencies on third-party libraries to perform functions such as logging, monitoring, input validation, form handling, and more.

Unfortunately, any bug in a third-party library becomes a bug in the application you deploy. This became uncomfortably real for the Java world in December 2021, as an LDAP injection flaw in the widely used Log4j 2 library forced JVMs around the world to go offline.

Various types of computer bugs covering scope, effect and severity
Types of bugs can be categorized in several ways depending on their context and their effect on the user.

One way to mitigate the possibility of software dependencies introducing runtime errors to applications is to use only approved libraries from organizations such as Apache or Eclipse.

Another protective measure is to regularly update an application’s dependencies to the latest version as soon as updates are available.

Finally, be aware of secondary or tertiary dependencies – those upon which your primary dependencies themselves rely – and be aware of the risks these entail.

In the world of software development, “perfect” is the enemy of “done”. No program is immune to the threat of an unexpected runtime error. However, when enterprise developers become aware of possible causes and take steps to mitigate potential threats, they can create software that minimizes the likelihood of encountering a runtime error.

Margie D. Carlisle