If you have a for loop like this:
for(j = 0; j<=90; j++){}
It works fine. But when you have a for loop like this:
for(j
for(j = 0; j<=90; j++){}
j++ means j=j+1, j value already 0 now we are adding 1 so now the sum value of j+1 became 1, finally we are overriding the j value(0) with the sum value(1) so here we are overriding the j value by j+1. So each iteration j value will be incremented by 1.
for(j = 0; j<=90; j+3){}
Here j+3 means j value already 0 now we are adding 3 so now the sum value of j+3 became 3 but we are not overriding the existing j value. So that JVM asking the programmer, you are calculating the new value but where you are assigning that value to a variable(i.e j). That's why we are getting the compile-time error " invalid AssignmentOperator ".
If we want to increment j value by 3 then we can use any one of the following way.
for (int j=0; j<=90; j+=3) --> here each iteration j value will be incremented by 3.
for (int j=0; j<=90; j=j+3) --> here each iteration j value will be incremented by 3.