The for-statement
Different loop-statements in Java
Java provides 3 types of loop-statements:
1. The for-statement
2. The while-statement
3. The do-while-statement
The for-statement (1)
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
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The for-statement is ideally suited for making the following type of
program:
Let some variable x take on a series of value one at a time
For each value taken on by a variable x, the body of the for-statement
is executed once.
repeat ( for x = 1, 2, 3, .... 10 )
execute this statement;
The for-statement (2)
Flow chart of a for-statement
The most common way to use a forstatement (2)
The most common way to use a forstatement (3)
public class For01
{
public static void main(String[] args)
{
int a;
for ( a = 1 ; a <= 10 ; a = a + 1 )
{
System.out.println(a); // Print a
}
System.out.println("Done");
}
}
The most common way to use a forstatement (1)

The for-statement was originally invented to let some variable take on
a series of value
for ( var = START_VALUE ; var <= STOP_VALUE ; var = var + INCR )
{
/* for-body (statements) */
}

For each of the value, the statements in the for-body are executed
Flow chart of this program:
Programming example 1: find all
divisors of a number (1)

Write a Java program that reads in an integer n... and prints all its
divisors
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Input: n = 12
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Output: 1, 2, 3, 4, 6, 12
Programming example 1: find all
divisors of a number (2)

Check if 12 is divisible by 1

Check if 12 is divisible by 2

...

Check if 12 is divisible by 12

We do not need to check numbers > 12 because only number ≤ 12 can
be divisors !
Programming example 1: find all
divisors of a number (3)
for (x = 1, 2, 3, ...., 10) do
{
print x;
}
This notation can be converted to a for-statement very naturally:
for ( x = 1; x <= 10; x = x + 1 )
{
print x;
}
Programming example 1: find all
divisors of a number (4)
public class Divisors01
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
int n, x;
n = in.nextInt();
// Read in number
for ( x = 1; x <= n; x++ ) // Run x = 1, 2, ..., n
{
if ( n % x == 0 )
{ // x is a divisor of n
System.out.println(x);
}
}
}
}
Programming example 2: compute the
sum 1+2+3+...+n (1)
input: n = some integer number
sum = 0; // Clear the running total !
for ( x = 1, 2, 3, ..., n ) do
{
Add x to sum
}
Print sum;
Programming example 2: compute the
sum 1+2+3+...+n (2)
public class Divisors01
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
int n, x, sum = 0;
System.out.print("Enter a number n: ");
n = in.nextInt();
// Read in number
for ( x = 1; x <= n; x++ ) // Run x = 1, 2, ..., n
{
sum = sum + x; // Add x to sum
}
System.out.println(sum); // Print final sum
}
}
Programming example 3: compute
factorial n! (1)
Write a Java program that reads in an integer n... and prints the
factorial n! = 1×2×3×...×n
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
Input: n = 5
Output: 120 (because 1 × 2 × 3 × 4 × 5 = 120)
Programming example 3: compute
factorial n! (2)
input: n = some integer number
product = 1; // Set running product to 1
for ( x = 1, 2, 3, ..., n ) do
{
Multiply x into product
}
Print sum;
Programming example 3: compute
factorial n! (3)
public class Factorial01 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n, x, product = 1;
System.out.print("Enter a number n: ");
n = in.nextInt();
// Read in number
for ( x = 1; x <= n; x++ ) {
product = product * x;
// Multiply x into product
}
System.out.println(product); // Print final product
}
The break and continue statements
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Introduction
•
There are 2 special statements that can affect the execution
of loop statements (such as a for-statement)
•
The special statements are:
■ break
■ continue
•
We will study their meaning and how to use these special
statements inside the while-statement
Effect of the break and continue
statements on the for-statement (1)
The continue statement
•
Syntax:
continue;
Effect:
◦
When the continue statement is executed inside a loopstatement, the program will skip over the remainder of the
loop-body to the end of the loop body
◦
Note:
■ What happens next when the program reaches the
end of a loop depends on the type of loop
statement !!!
Effect of the break and continue
statements on the for-statement (2)