Java Reference
In-Depth Information
Infinite loop II
for( ; true; ); // Explicit true is used here
A
break
statement is used to stop the execution of a
for
-loop statement. When a
break
statement is executed,
the control is transferred to the next statement, if any, after the
for
-loop statement. You can rewrite the
for
-loop
statement to print all integers between 1 and 10 using a
break
statement.
for(int num = 1; ; num++) { // No condition-expression
System.out.println(num); // Print the number
if (num == 10) {
break; // Break out of loop when i is 10
}
}
This
for
-loop statement prints the same integers as the previous
for
-loop statement did. However, the latter is
not recommended because you are using a
break
statement instead of using the condition-expression to break out of
the loop. It is good programming practice to use a condition-expression to break out of a
for
loop.
Expression-list
The expression-list part is optional. It may contain one or more expressions separated by a comma. You can use only
expressions that can be converted to a statement by appending a semicolon at the end. Please refer to the discussion
on the expression statement in the beginning of this chapter for more details. You can rewrite the same example of
printing all integers between 1 and 10 as follows:
for(int num = 1; num <= 10; System.out.println(num), num++);
Note that this
for
-loop statement uses two expressions in the expression-list, which are separated by a comma.
A
for
-loop statement gives you more power to write compact code.
You can rewrite the above
for
-loop statement as follows to make it more compact and accomplish the same task:
for(int num = 1; num <= 10; System.out.println(num++));
Note that you combined the two expressions in the expression-list into one. You used
num++
as the argument
to the
println()
method, so it prints the value of
num
first, and then increments its value by 1. Can you predict the
output of the above
for
-loop statement if you replace
num++
by
++num
?
You can also use nested
for
-loop statements, that is,
for
-loop statements inside another
for
-loop statement.
Suppose you want to print a
3x3
(read as three by three) matrix.
11 12 13
21 22 23
31 32 33
