Java Increment and decrement

Using ++ and -- in Java

Java has two opposite operations called increment (++) and decrement (--), which increase or decrease the value of a variable by one.

int n = 10;
n++; // 11
n--; // 10

The code above is equivalent to the following:

int n = 10;
n += 1; // 11
n -= 1; // 10

Prefix and postfix forms

Both increment operator and decrement operator have two forms, which are very important when using the result in the current statement:

• the prefix form  (++n or --n) increases or decreases the value of a variable before it is used;
• the postfix form (n++ or n--) increases or decreases the value of a variable after it is used.

The following examples demonstrate both forms of increment.

Prefix increment:

int a = 4;
int b = ++a;

System.out.println(a); // 5
System.out.println(b); // 5

In this case, the value of a has been incremented and then assigned to b. So, the value of both a and b is 5.

Postfix increment:

int a = 4;
int b = a++;

System.out.println(a); // 5
System.out.println(b); // 4

In Java, the postfix operator has higher precedence than the assignment operator. However, it returns the original value of a, not the incremented one. That's why when we assign a++ to b, we actually assign 4, and then variable a is incremented. So, value of b is 4 and value of a is 5.

If that's still not clear enough for you, take a look at this code:

int a = 4;
System.out.println(a++ + a); // this is 9

We hope that now you fully understand the increment and decrement operations and their prefix and postfix forms.

Conclusion

Congratulations, you've just learned the fundamental operations in Java: increment (++) and decrement (--). These operations can be used in two forms: prefix (++n or --n), which modifies the value before its use in a statement, and postfix (n++ or n--), which modifies it after. Grasping these operations is vital due to their widespread use in many aspects of programming and program design.