Java, one of the most versatile programming languages of our time having been adopted by millions of developers around the world to build a variety of applications and software, mostly due to its simplicity and ease of use can become quite challenging when it comes to writing efficient code, whether written by an experienced developer or by someone who's just starting in this field.

in this article, I will explore five(5) of the most efficient ways you can write your Java program having tested this method in different scenarios, by following these tips you can improve the readability of your code, making it more effective and easy to maintain thereby achieving your goal without much hassle.

Use Appropriate Data Structures

choosing the right data structures can be a bit tricky and have either a good or bad impact on the performance of your code. for example, using an ArrayList instead of a LinkedList can result in faster access times for the collection of large data, let's say you have a list of integers, and you need to perform some operations on it, such as finding the sum of all the elements or searching for a particular element in the list. In this case, using an ArrayList might seem like an obvious choice, since it provides fast access times for indexed elements. However, if this list is very large, using an ArrayList can result in slow performance due to the time it takes to search through the list. a better option may be to use a HashSet. A HashSet provides fast lookup times for individual elements, making it ideal for operations like checking membership or searching. let's take a look at a practical example

import java.util.HashSet;

public class Example {
   public static void main(String[] args) {
      // Create a HashSet of integers
      HashSet<Integer> set = new HashSet<Integer>();

      // Add some elements to the set
      set.add(1);
      set.add(2);
      set.add(3);
      set.add(4);

      // Check if an element is in the set
      boolean contains = set.contains(4);
      System.out.println("Set contains 4? " + contains);

      // Calculate the sum of all elements in the set
      int sum = 0;
      for (int i : set) {
         sum += i;
      }
      System.out.println("Sum of elements in the set: " + sum);
   }
}

here we create a HashSet of integers and add some elements to it, we then check if the set contains the element 4, which returns true, Finally, we calculate the sum of all the elements in the set using for-each loop. since the HashSet provides fast access times for individual elements these operations are performed fast and efficiently.

Minimize Object Creation

Creating unnecessary objects can be an expensive operation in both memory and time. Minimizing object creation is therefore an important technique in optimizing memory and the performance of your code. One common way to minimize object creation is to reuse already created objects wherever possible, for example, if you need to create a lot of String objects that have the same value, you can reuse an existing String object instead of creating a new one each time. let's see a demonstration.

public class Example {
   public static void main(String[] args) {
      // Create a String object with the value "Hello, world!"
      String greeting = "Hello, world!";

      // Reuse the same String object in a loop
      for (int i = 0; i < 10; i++) {
         System.out.println(greeting);
      }
   }
}

here, Instead of creating a new String object each time we want to print the greeting in a loop, we reuse the same String object by referencing the variable greeting. This saves memory and time since we only need to create the String object once.

Another way to do this is to avoid creating temporary objects that are used only once For example, instead of creating a new Integer object to increment a variable, you can simply use the ++ operator.

public class Example {
   public static void main(String[] args) {
      // Initialize a variable
      int count = 0;

      // Increment the variable without creating a temporary object
      count++;

      // Print the value of the variable
      System.out.println("Count: " + count);
   }
}

we initialize a variable count to 0. Instead of creating a new Integer object to increment the variable, we simply use the ++ operator. This avoids creating a temporary object and improves the performance of our code.

Use efficient flow constructs

Using efficient control flow constructs can help improve the readability and performance of your code. For example, using a switch statement instead of a long chain of if-else statements can result in faster execution times. One commonly used flow control construct in Java is the switch statement, which allows you to test a variable against multiple values and execute different code blocks based on the result. However, using a switch statement with a large number of cases can lead to slow performance, one way to optimize switch statements is to use the HashMap data structure to map the cases to corresponding actions. This approach can significantly improve performance by reducing the time it takes to find the correct code block to execute. lets take a look.

import java.util.HashMap;

public class Example {
   public static void main(String[] args) {
      // Create a HashMap to map cases to actions
      HashMap<Integer, Runnable> actions = new HashMap<>();
      actions.put(0, () -> System.out.println("Case 0"));
      actions.put(1, () -> System.out.println("Case 1"));
      actions.put(2, () -> System.out.println("Case 2"));
      actions.put(3, () -> System.out.println("Case 3"));

      // Test a variable against the cases using the HashMap
      int i = 1;
      actions.getOrDefault(i, () -> System.out.println("Default case")).run();
   }
}

Here we create a HashMap to map cases to corresponding actions. We add some cases to the HashMap using lambda expressions that print a message for each case. We then test a variable i against the cases using the getOrDefault method of the HashMap. If the key is found in the HashMap, the corresponding action is executed. If the key is not found, a default action is executed.

Optimize Loops

Loops can be a common source of performance issues in Java programs. To optimize loops, avoid doing unnecessary work inside the loop, minimize the number of loop iterations, and consider using a more efficient loop construct (such as a for-each loop instead of a traditional for loop), one way to do this is to move loop-invariant code outside the loop. Loop-invariant code is code that does not depend on the loop variable and therefore does not need to be executed repeatedly.

public class Example {
   public static void main(String[] args) {
      // Initialize an array of integers
      int[] array = {1, 2, 3, 4, 5};

      // Calculate the sum of the array using a loop
      int sum = 0;
      for (int i = 0; i < array.length; i++) {
         sum += array[i];
      }
      System.out.println("Sum: " + sum);

      // Calculate the sum of the array using a loop with loop-invariant code outside the loop
      sum = 0;
      int len = array.length;
      for (int i = 0; i < len; i++) {
         sum += array[i];
      }
      System.out.println("Sum: " + sum);
   }
}

In this example, we calculate the sum of an array of integers using a loop. In the first loop, we initialize the sum to 0 and add each element of the array to the sum within the loop. In the second loop, we move the length of the array outside the loop and store it in a separate variable len. Since the length of the array is loop-invariant, it does not need to be calculated repeatedly within the loop.

Another way is to use a more efficient loop construct when possible, like using a for-each loop or an iterator this can be more efficient than using a for-loop in certain situations. Here's an example.

import java.util.ArrayList;
import java.util.Iterator;

public class Example {
   public static void main(String[] args) {
      // Initialize an ArrayList of strings
      ArrayList<String> list = new ArrayList<>();
      list.add("One");
      list.add("Two");
      list.add("Three");

      // Iterate over the ArrayList using a traditional for loop
      for (int i = 0; i < list.size(); i++) {
         System.out.println(list.get(i));
      }

      // Iterate over the ArrayList using a foreach loop
      for (String s : list) {
         System.out.println(s);
      }

      // Iterate over the ArrayList using an iterator
      Iterator<String> iterator = list.iterator();
      while (iterator.hasNext()) {
         System.out.println(iterator.next());
      }
   }
}

Here we initialize an ArrayList of strings and iterate over it using three different loop constructs: a traditional for-loop, a for-each loop, and an iterator. The for-each loop and iterator are more efficient than the traditional for-loop since they avoid the need to calculate the length of the ArrayList and retrieve elements by index.

Use the right libraries and APIs

Choosing the right libraries and APIs can make a big difference in the performance of your code. For example, using the StringBuilder class instead of the String class for string concatenation can be more efficient, and using the Java NIO library instead of the traditional I/O API can result in faster I/O operations. lets see a demonstration.

public class Example {
    public static void main(String[] args) {
        String original = "Hello";
        String result = "";

        // Concatenate strings using the String class
        for (int i = 0; i < 10000; i++) {
            result += original;
        }

        // Concatenate strings using the StringBuilder class
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 10000; i++) {
            sb.append(original);
        }
        String optimizedResult = sb.toString();

        // Compare the results
        System.out.println(result.equals(optimizedResult)); // true
    }
}

Here we have two loops that concatenate a string "Hello" 10,000 times. The first loop uses the String class and the + operator to concatenate the strings. The second loop uses the StringBuilder class and the append() method to concatenate the strings.

When we run this code, we can see that the result of the two methods is the same (the strings are equal). However, the time taken to concatenate the strings is different. Using the String class and + operator can be slow and inefficient, especially when concatenating large numbers of strings. This is because every time we use the + operator, a new String object is created.

On the other hand, using the StringBuilder class and append() method is more efficient. This is because StringBuilder is designed to handle string manipulation and does not create a new String object every time we use the append() method. Instead, it modifies the same StringBuilder object in memory, resulting in faster and more efficient code.

Conclusion

I have listed five(5) crucial ways to increase the performance of your Java program, although it may take a while to fully get the hang of all of them I encourage fellow developers to adopt these methods, the practical difference between the conventional way and using these methods is quite stunning and could potentially further your desire to build large scale programs. Thank you for reading.