Difference between i++ vs ++i in java

Here we will learn difference between difference between post increment and pre increment:

i++ vs ++i
understand the concept of pre increment and post increment with proper examples.

Lets consider, int i = 100;

Now, keep track of values of both i and x as shown below

And now try to concentrate on the difference between i++ (post increment) and ++i (pre-increment)

Post increment

int i = 100;

int x = i++;

Here,

value of i will first be assigned to the variable x, and
then its original value will be incremented.

That's why its referred to as post increment operation which means do the task first and then increment.

So, x = 100, because value of i is assigned to x first and then i++ happens and the value of i is incremented by 1. Thus i = 101.

If you use system.out.print statement at this moment to print value of x & i, then you will get value of:

x=100 & i=101.

Pre increment

int i = 100;

int x = ++i;

Here

value of i will first be incremented by 1, and
then the incremented value will be assigned to x.

That's why its referred to as pre-increment operation which means increment the value first and then perform the task with incremented value.

So, x = 101, because the value of i is incremented first and then assigned to x.

And obviously, i = 101.

If you use system.out.print statement at this moment to print value of x & i, then you will get value of:

x=101 & i=101.

Go through the example to develop better understanding :

Find the value of x when i = 1;

1) int i = 1;

int x = i++; // here value of, x = 1 and i = 2

int y = ++i; // Now value of i=2 so ++i will increment the i(=3) by 1 and assign it to y(=3)

System.out.println("Value of x = "+ x);

System.out.println("Value of y = "+ y);

OUTPUT

Value of x = 1

Value of y = 3

Example program for i++ vs ++i

See the java code below and guess the output for better understanding of i++ vs ++i java:

package basic;

public class PrePostIncrementOperator {

      public static void main(String[] args) {
            int i = 0, j=0;
            int x = i++;  //Here i=1 but x=o(initial value of i)
            System.out.println("x: "+ x +" i: "+ i); 
           
            int y = ++j;
            System.out.println("y: "+ y +" j: "+j);
      }

}

OUTPUT

x: 0 i: 1
y: 1 j: 1

So in both the case we see that value of the variable(i&j) is getting incremented. The difference is in the process of assigning the value.

i++ assigns non-incremented value to x. whereas

++j assigns the incremented value to y.

Hope I have been able to explain the concept clearly to you.

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About the Author

Rohanjit Kumar
Technology geek, loves to write and share knowledge with the world. Having 9+ years of IT experience. B.Tech in Computer Science & Engineering

Page Views : Published Date : Jun 28,2020

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