Item Use native methods wisely

The Java Native Interface (JNI) allows Java programs to call native methods written in languages ​​such as C or C. Historically, native methods had three main uses:

• Access platform-specific features such as logs.
• Use native code libraries, including legacy ones, to access old data.
• Write performance-critical parts of applications in native languages ​​to improve performance.

However, as the Java platform has matured, the need to use native methods to access platform-specific functionality has decreased. Many of these features are now accessible directly on the Java platform, such as the Processes API, added in Java 9, which provides access to operating system processes. It is still acceptable to use native methods to access native libraries when there are no Java equivalents, but this practice must be carefully considered.

When it comes to improving performance, using native methods is rarely advisable. In early versions of Java this was necessary, but JVMs have evolved and become much faster. Nowadays, most tasks can be performed with similar performance in pure Java. An example of this is the reimplementation of the BigInteger class. Initially, BigInteger depended on a multi-precision arithmetic library written in C, but with the evolution of the JVM, the version implemented in Java became as efficient as the native one.

However, there are cases where extreme performance may still justify the use of native methods. An example is the use of the GMP library (GNU Multiple Precision Arithmetic Library) for programmers who require high precision arithmetic, where native methods may be the best choice.

It is important to be aware of the consequences of using native methods. Because native languages ​​do not have the same security guarantees as Java, they introduce risks such as memory corruption. Additionally, using native methods reduces code portability, making it more dependent on the specific platform. The process of debugging native code is also more complicated and, if not done well, can end up decreasing the program's performance due to the cost of transitioning between Java and native code.

Another crucial point is that native methods require the use of "glue code", which is often difficult to read and tedious to write. This adds an extra layer of complexity to development, which increases the likelihood of bugs that are difficult to identify and fix.

In short, think very carefully before using native methods. In most cases, you won't need to use them to improve performance. If there is a need to access low-level resources or native libraries, limit the use of native methods to a minimum, keep native code small, and test it thoroughly to avoid serious problems that could compromise the entire application.

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