Arithmetic Operators
Arithmetic operators are used to perform common mathematical operations.
| Operator | Name | Description | Example | Try it |
|---|---|---|---|---|
| + | Addition | Adds together two values | x + y | |
| - | Subtraction | Subtracts one value from another | x - y | |
| * | Multiplication | Multiplies two values | x * y | |
| / | Division | Divides one value by another | x / y | |
| % | Modulus | Returns the division remainder | x % y | |
| ++ | Increment | Increases the value of a variable by 1 | ++x | |
| -- | Decrement | Decreases the value of a variable by 1 | --x |
Here is an example using different arithmetic operators in one example:
Example
int x = 10;
int y = 3;
System.out.println(x + y); // 13
System.out.println(x - y); // 7
System.out.println(x * y); // 30
System.out.println(x / y); // 3
System.out.println(x % y); // 1
int z = 5;
++z;
System.out.println(z); // 6
--z;
System.out.println(z); // 5
Note: When dividing two integers in Java, the result will also be an integer. For example,
10 / 3gives3. If you want a decimal result, usedoublevalues, like10.0 / 3. Example int a = 10; int b = 3; System.out.println(a / b); // Integer division, result is 3 double c = 10.0d; double d = 3.0d; System.out.println(c / d); // Decimal division, result is 3.333...
Incrementing and Decrementing
Incrementing and decrementing are very common in programming, especially when working with counters, loops, and arrays (which you will learn more about in later chapters).
The ++ operator increases a value by 1, while the -- operator decreases a value by 1:
Example
int x = 5;
++x; // Increment x by 1
System.out.println(x); // 6
Example
int x = 5;
--x; // Decrement x by 1
System.out.println(x); // 4
Sometimes, you might both increment and decrement the same variable. Remember that if you increase a value and later decrease it, it will go up by one and then back down by one - ending up where it started:
Example
int x = 5;
++x; // Increment x by 1 (x becomes 6)
--x; // Decrement x by 1 (x becomes 5 again)
System.out.println(x); // 5
Real Life Example: Counting People
Imagine you are building a program to count how many people enter and leave a room. You can use ++ to increase the counter when someone enters, and -- to decrease it when someone leaves:
Example
int peopleInRoom = 0;
// 3 people enter
peopleInRoom++;
peopleInRoom++;
peopleInRoom++;
System.out.println(peopleInRoom); // 3
// 1 person leaves
peopleInRoom--;
System.out.println(peopleInRoom); // 2
