Chapter 1: The Scenario

In my professional experience, we encountered a piece of Java code that retrieves a String from a properties file. This String defines a package name that we utilize to build a file path. To illustrate, our code resembles the following:

final String myPackage = "com.dntech.demo";

final String samplePath = "myFolder" + "\\" + myPackage.replaceAll("\.", "\\") + "\\" + "myFile";

FileInputStream fileInputStream = new FileInputStream(samplePath);

The code begins with a prefix of "myFolder," followed by a path separator, where we substitute every dot in the package String with the path separator, ultimately appending the filename. This String is then used to access the desired file.

Upon committing the code from local development to the remote repository, we encountered a build failure. Can you deduce the reason behind this issue?

This predicament relates to cross-platform compatibility.

Our development team works on Windows machines. Once a developer finalizes their code, they push it to our BitBucket repository, which triggers an internal build pipeline to compile the application. However, the build environment operates on Linux, not Windows.

To remedy this, we utilized the Java File library to obtain the appropriate path separator, allowing the JVM to select the correct separator based on the operating system:

final String PATH_SEPARATOR = File.separator;

final String myPackage = "com.dntech.demo";

final String samplePath = "myFolder" + PATH_SEPARATOR + myPackage.replaceAll("\.", PATH_SEPARATOR) + PATH_SEPARATOR + "myFile";

FileInputStream fileInputStream = new FileInputStream(samplePath);

Simple enough, right? Let's execute the application locally...

Wait, an error has occurred? The message reads: "Exception in thread 'main' java.lang.IllegalArgumentException: character to be escaped is missing."

Take a moment to think. Can you identify the issue?

In Windows, the path separator is a backward slash (""). This character has a dual role in Regular Expressions as an escape character, which can lead to complications. When invoking the replaceAll() method, the backslash is interpreted as an escape character, which necessitates a following character to escape.

The documentation for the Matcher.java replaceAll() method emphasizes this point:

"Note that backslashes (`) and dollar signs (`$) in the replacement string may yield results different from a literal replacement. Dollar signs may refer to captured subsequences, and backslashes serve to escape literal characters."

So, how can we resolve this?

Rather than using regular expressions for character replacement, we can simply employ a character sequence by using replace() instead of replaceAll():

final String samplePath = "myFolder" + PATH_SEPARATOR + myPackage.replace(".", PATH_SEPARATOR) + PATH_SEPARATOR + "myFile";

With this adjustment, the output is now correct, and the application functions seamlessly across platforms.

I hope you found this article insightful. If you share my enthusiasm for learning Java and delving into backend engineering, consider following my channel for updates on my daily work and life inspirations.

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Chapter 2: Video Resources

In this video, titled "Fix the 'Expected a Step on Line' error in Jenkins," we will explore common pitfalls that can lead to build failures and how to address them effectively.

The second video, "Update Test Cases Result in Azure Dev Ops via Pipeline | Code | YAML," provides insights into managing test cases in Azure DevOps, offering practical solutions to streamline your development process.