Question

Why does Java provide the ability to call from a Java program native methods that are written in, say, C or C++? Provide an example of a situation in which a native method is useful.

Answer 1

Actually we must first know that all programs written in Java are intended to be platform I/O independent means that we can run those Java programs almost on any platform be it C, C++, Windows, etc. Hence, following are the reasons why Java provides ability to call native methods from a Java program:

• Unfortunately, the Java language does not provide facilties like accessing various system resources such as reading/writing from/to Input-Output devices or ports. So, that is why Java provides the ability to use native methods. Hence, an example of situation where using a native method is useful is when we want to perform such system specific I/O operations such as reading, writing from/to Input-Output devices or ports. So, to use such features we must first have to write program codes in a language that supports the above features like system specific I/O operations (like C/C++). The crux is that Java provides the ability to call from a Java program, native methods that are written in some other language like C/C++ just to increase the code functionality and extend its execution to different platforms, thus making the Java programs platform independent. The main purpose of native methods is to interface with system calls or libraries that are written in other programming languages in order to make direct system calls, which is not provided by the Java language itself. However, we must know that if a Java program calls a native method that is written in some other language like C/C++, then it won't remain architecture-neutral anymore.
• Also, another reason is that, Java, as we know is an object-oriented language and it offers the concept of code reusabilty. Hence, Java allows calling such native methods that are written in some other programming language to implement code reusability in order to save time of the user.
• Another reason is that using native methods allows a user to write codes that perform much faster due to better CPU assembly instructions being present in the native methods that belong to languages like C/C++. Hence, the user can easily use these native methods in case he/she wants to write a code for a time-critical part of the program where high execution speed is important and the program is required to run and perform operations/output in minimum possible time.

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