Try writing each of these for loops yourself before reading the solutions.
Count up from to :
for (int i = 1; i <= 10; i++) {
System.out.println(i);
}
Count down from to :
for (int i = 10; i >= 1; i--) {
System.out.println(i);
}
Count by s from to :
for (int i = 0; i <= 20; i += 2) {
System.out.println(i);
}
Notice the pattern. To count up, you start low, use < or <=, and increment. To count down, you start high, use > or >=, and decrement. To skip values, change the update step from i++ to i += step.