Variables#

A variable is just a container that we can store a value in that has a specific name. The name can be anything we want, and so can the value. The ImageJ Macro language is very friendly: there is no need to specify what we want to store in a variable, we can just assign it a value.

First variables#

In the examples below, you can click on the `+` icon and see hints and tips.

Let's create some variables:

// For example, we can store the value "42", under the name "number"
number = 42; // (1)!

// (2)!
// But a variable can also represent text (aka "string")
message = "This is also a variable";

// Verify the value of a variable by printing to the console
print(message);  // (3)!

1. Never forget the semi-colon ;!
2. While we are here, // is how your add comments to your code!
3. You should remember this piece of code from the previous exercise. However, instead of asking it to print "Hello World", we will be printing whatever is stored in the variable message!

Bad example#

Keep in mind that the name and value of a variable do not have to match. We could easily write the following code:

number = "Hello world";
dog = "Cat";
xyz_63193 = 42;

Why might we not want to do this? :shrug:

Changing a variable value#

We can change the value assigned to a variable name by assigning a new value to the same variable name:

message = "This is a message";
print(message);
message = "This is a new message";
print(message);

What happens when you run this code?

Once you have defined a variable, you can simply do math with it.

number = 15.6;

// Addition
number = number + 3;
print(number);

// Multiplication
new_number = number * 3;
print(new_number);

// Increment
counter = 0;
counter = counter + 1;
counter++;
print(counter);