difference between java ++ +1 code example

Example 1: ++i vs i++ java

int i = 3;
int a = i++; // a = 3, i = 4
int b = ++a; // b = 4, a = 4

Example 2: ++i vs i++ java

int a = 0;
int b = a++; // b = 0; a = 1

a = 0;
b = ++a: // b = 1; a = 1