Unit 1: Increment and Decrement
Table of Contents
Increment and Decrement
Other operations that come up often in computer science is increment and decrement (adding 1 and subtracting 1).
Increment operator: ++
Decrement operator: --
Note that the increment and decrement operators are unary operators, which mean they operate on 1 thing (arithmetic, assignment, and augmented assignment operators are all binary operators).
There are 2 types of increment and decrement: post and pre. These determine when the variable is incremented or decremented. Analyze the code below.
int i = 1;
int j;
// pre-increment
j = ++i; // increment i, then assign that to j
System.out.println("j: " + j + ", i: " + i);
// post-increment
i = 1; // reset
j = i++; // assign i to j, then increment i
System.out.println("j: " + j + ", i: " + i);
// pre-decrement
i = 1; // reset
j = --i; // decrement i, then assign that to j
System.out.println("j: " + j + ", i: " + i);
// post-decrement
i = 1; // reset
j = i--; // assign i to j, then decrement i
System.out.println("j: " + j + ", i: " + i);
Output:
j: 2, i: 2
j: 1, i: 2
j: 0, i: 0
j: 1, i: 0
Note that pre-increment and pre-decrement puts the ++ or -- before the variable name, while post-increment and post-decrement puts the ++ or -- after the variable name.
Note: If you are simply incrementing or decrementing a variable and not doing anything else, post- and pre-increment or decrement won’t matter. You only need to be careful when you’re mixing a bunch of operators.