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Inappropriate coding practices - Unnecessary imports

Need​

Elimination of unnecessary imports to optimize resource usage

Context​

  • Usage of Java for building robust and scalable applications
  • Usage of javax.servlet for building Java web applications
  • Usage of javax.servlet.http for handling HTTP requests and responses in Java Servlets
  • Usage of java.io for input and output operations in Java

Description​

Non compliant code​

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*; // Unnecessary import

public class HelloWorldServlet extends HttpServlet {
    
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        
        PrintWriter out = response.getWriter();
        out.println("Hello World");
        
    }
}

In the code snippet above, we have a simple Java servlet that responds to HTTP GET requests by writing "Hello World" to the response.

However, the java.util.* package is imported at the beginning of the file, even though none of its classes or interfaces are used anywhere in the code. This is an example of an unnecessary import, which is a bad coding practice.

Unnecessary imports can lead to several problems:

  1. They can make the code harder to understand and maintain. Other developers who look at the import statements might spend time trying to figure out where in the code the imported classes or interfaces are used.

  2. They can increase the memory footprint of the application. When a Java class is loaded, all its static initializers are run and its static fields are allocated memory. Even though the impact on performance is usually negligible, it's still a waste of resources.

  3. They can lead to name conflicts. If a class with the same name is added to another imported package in the future, it might lead to a compilation error.

  4. They can make the code more prone to errors. If a class with the same name is added to another imported package in the future, and this class is used in the code, it might lead to subtle bugs that are hard to detect.

For these reasons, it's a good practice to remove unnecessary imports from your code.

Steps​

  • Identify and remove any unnecessary imports in the code.
  • Review the code and determine which modules are actually used.
  • Remove any imports that are not used in the code.
  • Ensure that the code still functions correctly after removing the unnecessary imports.

Compliant code​

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class HelloWorldServlet extends HttpServlet {
    
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        
        PrintWriter out = response.getWriter();
        out.println("Hello World");
        
    }
}

The original code had an unnecessary import statement - import java.util.*;. This import statement was not required as none of the classes or interfaces from the java.util package were being used in the code.

In the fixed code, this unnecessary import statement has been removed. The remaining import statements are necessary for the code to function correctly.

  • javax.servlet.* and javax.servlet.http.* are required for the servlet functionality, such as HttpServlet, HttpServletRequest, and HttpServletResponse.
  • java.io.* is required for handling input-output operations, in this case, for using PrintWriter.

Removing unnecessary imports helps in reducing the load time and memory usage of the application. It also improves the readability and maintainability of the code, as it's easier to understand which packages are actually being used.

After removing the unnecessary import, it's important to ensure that the code still functions correctly. In this case, the code should still display "Hello World" when the doGet method of the HelloWorldServlet is called.

References​

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