Subtraction in Java: Method, Code & Examples

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  • 0:04 Subtraction in Java
  • 1:44 Different Data Types
  • 3:18 BigDecimal
  • 4:17 Lesson Summary
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Lesson Transcript
Instructor: Martin Gibbs

Martin has 16 years experience in Human Resources Information Systems and has a PhD in Information Technology Management. He is an adjunct professor of computer science and computer programming.

Arithmetic operations are a core function of any programming language. This lesson will describe methods for subtraction in Java, providing working code examples.

Subtraction in Java

Java allows for a wide range of arithmetic operations, from the simplest calculation to the most complex algorithm. Before we can begin writing programs that calculate lens settings for space telescopes, we need to start at the beginning. This lesson will cover subtraction in Java, but it also helps to be aware of the other arithmetic operators available.

In Java, the operators used to perform math are laid out on the table shown below:

Operator Function
- Subtract
+ Add
* Multiply
/ Divide
% Modulo/Remainder

As you can see, the symbols are rather self-explanatory, except for the percent symbol (%) which, as you can see, refers to a modulo or a remainder. Let's take a look at a straightforward subtraction operation. We're going to subtract 1 from an integer value (a counter), and display the output, which you can see below:

int counter = 15;
counter = counter - 1;
System.out.println("Subtraction = " + counter);

When this code runs, the next output is displayed which, as you can see, has the subtraction value placed at 14:

Java subtraction basic output

Java fully supports more complex statements with multiple arithmetic operations. Just as you learned in math, the order of operations is important. Make sure the parenthesis around your statements are placed properly; after all, Java will only do what you tell it to do! For example, the code shown below first subtracts 1 from the counter, then subtracts the enrolled variable from this result:

int counter = 15;
int enrolled = 3;
counter = (counter - 1) - enrolled;

A good habit is to desk-check your equations by plugging in some sample numbers, then making sure you get the result you expect. In this example, the result should be 11: (15-1) - 3.

Java subtraction complex output

As you can see, the counter value is placed at 11.

So far, we've been working with integers. What if you have a mix of data types?

Different Data Types

So what happens if you try to subtract numbers of a different data type? It depends on the data types involved. For example, it's totally okay to subtract an int from a double or float, since those data types will maintain the precision. Therefore, the code shown below will compile and run just fine, returning a value of 37.34 (52.34 - 15).

int counter = 15;
double price = 52.34;
price = price - counter;

But remember: you can't create an integer value and subtract doubles from it. In other words, this will cause compiler errors, like the one you can see below:

counter = counter - price;

In fact, most developer tools will stop you right away. The image below is what the code looks like in the tool:

Java subtract double from int error

If you have mixed variable types, it would be a good idea to convert them up to the data type with the most precision, or try to perform subtraction on variables that are all the same type. In this case, we'd convert our integer values to double and then perform the subtraction. This helps eliminate some nasty surprises in the code.

While a little more complex, we can change our primitive integer value into an instance of the Integer class. This will let us access the doubleValue() method and thus convert the integer to a double. You can see this playing out in the code shown below:

int counter = 15;
double price = 52.34;
//create instance of Integer
Integer counter2 = new Integer(counter);
double counterD = counter2.doubleValue();
price = price - counterD;
System.out.println("Double minus int: " + price);

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