1. TK1114 Computer Programming
7 - while loop
TK1114 Computer Programming

2. Repetition Statements (Loop)
Repetition statements allow us to execute a statement multiple times
Java has three kinds of repetition statements:
the for loop
the while loop
the do-while loop
The programmer should choose the right kind of loop for the situation

3. for loop An example : for (initialization; condition; increment){
statement
true
condition
evaluated
false
increment
initialization
for (initialization; condition; increment){
statements; }
An example :
for (int count=1; count <= 5; count++){
System.out.println (count); }

4. while Loop while ( condition ){ statement; } An example:
true
false
condition
evaluated
while ( condition ){
statement; }
An example:
int count = 1;
while (count <= 5) {
System.out.println (count);
count++; }

5. do Loop An example : do { statement; } while ( condition )
true
condition
evaluated
statement
false
do {
statement; }
while ( condition )
An example :
int count = 0;
do {
count++;
System.out.println (count);
} while (count < 5);

6. Keep Positive Problem Description
Write a program that reads an unspecified number of integers, determines how many positive value have been read. Your program ends with the input 0.
Input
The data set consists of a list of positive integer, num (0 < num ≤ 100) that ends with 0.
Output
There is only one output for this problem, which is the number of integers positive.
Sample Input Output
Sample Input
Sample Output 6

7. Keep Positive import java.util.Scanner; public class KeepPositive{ 2
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int num;
int count = 0;
do {
num = sc.nextInt();
if (num > 0)
count++;
} while (num != 0);
System.out.println(count); } 2 -3 4 -5 6 7 -8 9 10 6

8. Min Max Problem Description
Write a program that reads 10 integers. Find the smallest and largest numbers.
Input
10 integers num (0 < num ≤ 100).
Output
The smallest and largest integer.
Sample Input Output
Sample Input
Sample Output
1 27

9. Min Max import java.util.Scanner; public class KeepPositive{ 12
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int num;
int max = 0, min = 100;
for (int count = 0; count<10; count++) {
num = sc.nextInt();
if (num > max)
max = num;
if (num < min)
min = num; };
System.out.println(min + " " + max); } 12 3 2 5 4 27 1 9 10 7
1 27

10. Sum of digits of numbers
Problem Description
Write a program to ask user for a positive integer and calculating sum of its digits then.
Input
integer positive number (n1>0 ).
Output
Sum of the digits.
Sample Input Output
Sample Input
Sample Output
 123 6

11. Sum of digits of numbers
Analysis
Input: 123
Output: = 6
We can use modulo operator to solve this problem.
123 % 10 = 3
123 / 10 = 12
12 % 10 = 2
12 / 10 = 1

12. Sum of digits of numbers
public class KeepPositive{
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int num, lastnum=0, sum=0;
num = in.nextInt();
if (num>0){
while (num != 0){
lastnum = num % 10;
sum += lastnum;
num /= 10; }
System.out.println(sum);
123 6

13. Area of a circle Problem Description
Write a program to calculate the area of a circle.
Input
The first line of input is the number of input n, where 1 ≤ n ≤ 20. For each of the following n lines there are radius for the circle.
Output
For each input, print the area.
Sample Input Output
Sample Input
Sample Output 4 3 34 12
28.26
452.16
50.24

14. Area of a circle import java.util.Scanner; public class Trial {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
double radius;
double area;
int n;
n = sc.nextInt();
for (int i=0; i<n; i++){
radius = sc.nextDouble();
area = radius * radius * 3.14;
System.out.println (area); }