Can Final Variables Be Changed? Understanding the Limits in Programming

What Are Final Variables?

Well, if you've ever written code in Java or a similar language, you've probably encountered the term final variables. I know I did when I first started, and I was a little confused about how they work. Simply put, a final variable is one whose value, once assigned, cannot be changed. But there's a bit more nuance to this than you might think. So, can final variables really never be changed? Let’s dive into this!

In Java, for example, declaring a variable as final means that its value is constant throughout its lifetime. The main idea behind this is to ensure that the variable behaves predictably once it has been initialized. This gives the developer peace of mind, knowing that the value won’t be altered accidentally.

But, as with most things in programming, there's always a bit more complexity under the surface.

Can Final Variables Be Modified?

The Short Answer: No

Honestly, when I first learned about final variables, I thought they were entirely unchangeable — like a rock in the ground. Once you assign a value to them, it stays locked in. And yes, that's mostly true. A final variable in Java, or similar languages, cannot be reassigned after its initial assignment. This is especially true for primitive types, such as int, double, and boolean.

But there’s a catch — and I’ll get to that in a minute.

What About Final Objects?

Here’s where things get a little tricky. If a final variable is an object reference (say, a String or an instance of a class), you can’t change the reference itself, meaning you can’t point the variable to a new object. However, the object’s state can still be modified.

For example, if you declare a final variable like this:

java
final StringBuilder sb = new StringBuilder("Hello");

You can’t assign a new StringBuilder to sb:

java
sb = new StringBuilder("World"); // This will throw an error!

But you can modify the internal content of the object:

java
sb.append(" World"); // This is fine!

So, in a sense, the reference to the object remains constant, but the contents of the object it refers to can change.

Why Would You Use Final Variables?

You might be wondering, why bother with final variables if they can be tricky? Well, let me tell you, they have their advantages.

For one, final variables help you avoid bugs by making certain values immutable. For example, once you assign a value to a constant like final int MAX_USERS = 100;, you don't have to worry about someone accidentally changing it down the line. It’s a safeguard against unintended side effects, especially in large codebases.

A friend of mine, who’s been coding for years, told me how final variables saved him from a headache on a recent project. He was working on a system where the number of users was critical, and by using a final variable for MAX_USERS, he was able to guarantee that no part of the code would change this value without noticing.

When Can Final Variables Be Changed? (Kind Of…)

Final Variables and Reflection

Now, here’s something that may surprise you. Technically speaking, final variables can be modified under certain conditions, especially if you use reflection in Java. Reflection is a powerful tool that allows you to inspect or modify the properties of classes at runtime. So, using reflection, you can change the value of a final variable — but don’t get any ideas, as this goes against the spirit of using final in the first place.

Here’s a small example using reflection to change a final variable:

java
import java.lang.reflect.Field;public class Main { public static void main(String[] args) throws Exception { final String finalVar = "Hello"; Field field = finalVar.getClass().getDeclaredField("value"); field.setAccessible(true); field.set(finalVar, "Changed".toCharArray()); System.out.println(finalVar); }}

This code manipulates the internal value of a final variable. However, I should mention that using reflection to modify final variables is not recommended, as it goes against best practices and can lead to unpredictable behavior. So while it’s technically possible, it’s really not a good idea unless you absolutely know what you’re doing (and trust the code you’re working with).

The Moral of the Story: Final Variables Are Safe… Mostly

So, to sum up what we’ve learned, final variables can’t be changed in the traditional sense (i.e., reassigned). However, if the variable is a reference to an object, the object’s state can be altered. This makes final variables particularly useful for ensuring that critical data is protected from accidental changes, but still allowing the internal contents of objects to evolve.

That said, there’s always a loophole through reflection, but again, I wouldn’t recommend going down that rabbit hole unless you absolutely need to.

Conclusion: Should You Use Final Variables?

Honestly, final variables are incredibly useful in programming — and especially in languages like Java — because they give you more control and prevent errors by locking certain values. They’re perfect for constants, configuration settings, and any value you want to ensure remains unchanged throughout the code.

But don’t forget, you can’t just use them blindly. Be mindful of whether you need a variable to be truly immutable (like primitive types) or if you’re dealing with an object reference (where you might still change the state of the object).

In the end, it’s all about understanding the balance between safety and flexibility. And if you remember that, final variables will serve you well.

Is 165 cm normal for a 15 year old?

The predicted height for a female, based on your parents heights, is 155 to 165cm. Most 15 year old girls are nearly done growing. I was too. It's a very normal height for a girl.

Is 160 cm too tall for a 12 year old?

How Tall Should a 12 Year Old Be? We can only speak to national average heights here in North America, whereby, a 12 year old girl would be between 137 cm to 162 cm tall (4-1/2 to 5-1/3 feet). A 12 year old boy should be between 137 cm to 160 cm tall (4-1/2 to 5-1/4 feet).

How tall is a average 15 year old?

Average Height to Weight for Teenage Boys - 13 to 20 Years

How to get taller at 18?

Staying physically active is even more essential from childhood to grow and improve overall health. But taking it up even in adulthood can help you add a few inches to your height. Strength-building exercises, yoga, jumping rope, and biking all can help to increase your flexibility and grow a few inches taller.

Is 5.7 a good height for a 15 year old boy?

Generally speaking, the average height for 15 year olds girls is 62.9 inches (or 159.7 cm). On the other hand, teen boys at the age of 15 have a much higher average height, which is 67.0 inches (or 170.1 cm).

Can you grow between 16 and 18?

Most girls stop growing taller by age 14 or 15. However, after their early teenage growth spurt, boys continue gaining height at a gradual pace until around 18. Note that some kids will stop growing earlier and others may keep growing a year or two more.

Can you grow 1 cm after 17?

Even with a healthy diet, most people's height won't increase after age 18 to 20. The graph below shows the rate of growth from birth to age 20. As you can see, the growth lines fall to zero between ages 18 and 20 ( 7 , 8 ). The reason why your height stops increasing is your bones, specifically your growth plates.