Design Principles: {DRY, YAGNI, KISS}

Brief

Acronym	Expansion	Goal
DRY	Don’t Repeat Yourself	Avoid duplication of code
YAGNI	You Aren’t Gonna Need It	Don’t add functionality until it’s needed
KISS	Keep it short and Simple	Keep the code simple.

Details

DRY

Talks about avoiding code duplication in Software Development.

Example:

// Example of Code Duplication
public class EmployeeService {
  public void saveEmployee(Employee employee) {
      if (employee == null 
          || employee.name == null 
          || employee.name.isEmpty()) {
        throw new IllegalArgumentException("Employee Object is not valid");
      }
      // Save employee to database
  }

  public void updateEmployee(Employee employee) {
      if (employee == null 
          || employee.name == null 
          || employee.name.isEmpty()) {
        throw new IllegalArgumentException("Employee Object is not valid");
      }
      // Update employee in database
  }
}

Fix

public class EmployeeService {
  public void saveEmployee(Employee employee) {
      validateEmployee(employee);
      // Save employee to database
  }
  public void updateEmployee(Employee employee) {
      validateEmployee(employee);
      // Update employee in database
  }
  private void validateEmployee(Employee employee) {
      if(employee == null 
          || employee.name == null 
          || employee.name.isEmpty()) {
        throw new IllegalArgumentException("Employee Object is not valid");
      }
  }
}

YAGNI

Goal is to avoid adding functionality until it’s needed.
Example:

public class EmployeeService {
  public void saveEmployee(Employee employee) {
      validateEmployee(employee);
      // This is not needed now, but may be needed in future
      publishEmployeeForAnalytics(employee); 
      // Save employee to database
  }
}

Fix

public class EmployeeService {
  public void saveEmployee(Employee employee) {
      validateEmployee(employee);
      // Removed things that are not needed now
      // Save employee to database
  }
}

KISS

Keep it short and simple.
Goal is to keep the code clean and simple. Focuses on correctness, readability, and performance.
Correctness - Make it work first. Don’t worry about performance at this step.
Readability - Make it readable.
Performant - Make it performant. Optimize the code for performance.
Example:

public class StringUtils {
  public static String reverse(String str) {
      String reverse = "";
      for (int i = x.length() - 1; i >= 0; i--) {
          reverse += x.charAt(i);
      }
      return reverse;
  }
}

Fix

public class StringUtils {
  public static String reverse(String str) {
      return new StringBuilder(str).reverse().toString();
  }
}

References