1.3.1. Definite Loop¶

In Python the easiest way to write a definite loop is using the for loop in conjunction with the range function. For example:

for i in range(10):
   print(i)

In Java we would write this as:

for (int i = 0; i < 10; i++ ) {
    System.out.println(i);
}

In Python, the range function provides you with a wide variety of options for controlling the value of the loop variable.

range(stop)
range(start,stop)
range(start,stop,step)

The Java for loop is really analogous to the last option giving you explicit control over the starting, stopping, and stepping in the three clauses inside the parenthesis. You can think of it this way:

for (start clause; stop clause; step clause) {
    statement1
    statement2
    ...
}

If you want to start at 100, stop at 0 and count backward by 5 the Python loop would be written as:

for i in range(100,-1,-5):
    print(i)

In Java we would write this as:

for (int i = 100; i >= 0; i -= 5) {
    System.out.println(i);
}

1.3.2. Indefinite Loops¶

Both Python and Java support the while loop. Recall that in Python the while loop is written as:

while  condition:
   statement1
   statement2
   ...

In Java we add parenthesis and curly braces to get:

while (condition) {
    statement1
    statement2
    ...
}

Java adds an additional variation of the while loop called the “do while” loop. The do-while loop is very similar to while except that the condition is evaluated at the end of the loop rather than the beginning. This ensures that a loop will be executed at least one time. Some programmers prefer this loop in some situations because it avoids an additional assignment prior to the loop. For example:

do {
    statement1
    statement2
    ...
} while (condition);