Primitive Data and Definite Loops - Building Java Programs: A Back to Basics Approach - page 96

This code prints all of its output on a single line of output. Let's look at some code
that includes a combination of print and println to produce several lines of output:
for (int i = 1; i <= 6; i++) {
for (int j = 1; j <= 10; j++) {
System.out.print("*");
}
System.out.println();
}
When you write code that involves nested loops, you have to be careful to indent
the code correctly to make the structure clear. At the outermost level, the preceding
code is a simple for loop that executes six times:
for (int i = 1; i <= 6; i++) {
...
}
We use indentation for the statements inside this for loop to make it clear that
they are the body of this loop. Inside, we find two statements: another for loop and a
println . Let's look at the inner for loop:
for (int j = 1; j <= 10; j++) {
System.out.print("*");
}
This loop is controlled by the outer for loop, which is why it is indented, but it itself
controls a statement (the print statement), so we end up with another level of indenta-
tion. The indentation thus indicates that the print statement is controlled by the inner
for loop, which in turn is controlled by the outer for loop. So what does this inner
loop do? It prints 10 stars on the current line of output. They all appear on the same line
because we are using a print instead of a println . Notice that after this loop we per-
form a println :
System.out.println();
The net effect of the for loop followed by the println is that we get a line of output
with 10 stars on it. But remember that these statements are contained in an outer loop
that executes six times, so we end up getting six lines of output, each with 10 stars:
**********
**********
**********
**********
**********
**********