if(i == 0) ... //if i = 0 this will work and skip following statement
else if(i == 1) ...//if i not equal to 0 and if i = 1 this will work and skip following statement
else if(i == 2) ...// if i not equal to 0 or 1 and if i = 2 the statement will execute


if(i == 0) ...//if i = 0 this will work and check the following conditions also
if(i == 1) ...//regardless of the i == 0 check, this if condition is checked
if(i == 2) ...//regardless of the i == 0 and i == 1 check, this if condition is checked