Sentinelcontrolled while loop Java tutorial with PRACTICAL example

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Sentinel-controlled while loop - Java tutorial with a PRACTICAL example • Hi and welcome back to this channel • Today we are going to have a look at another form that a while loop may take in a program. • Previously we talked about counter-controlled loops • In this video particularly we will talk about another form of while loops which is called the Sentinel-controlled while loop • This while loop form is often used when you do not know exactly how many times a set of statements needs to be executed • But instead, you do know that the statements need to be executed until a special value is met. • This special value is called a sentinel • The portion of code on the screen is a typical example of a Sentinel-controlled while loop • int sentinel = 100; • int score =0; • while (score != sentinel) { • System.out.print( score + “ “); • score = score + 20; • } • In this example, we have started by declaring and initializing the Sentinel variable, here sentinel • Next, we have initialized the loop control variable score as well • In the while statement, we are using the loop condition to test the loop control variable score against the Sentinel variable sentinel • As long as, the loop control variable is different from the sentinel then the action statement will execute • The first action statement will output the values of the variable score • And the second action statement will increment the value of the variable score by 20, whenever the loop condition is met • Let’s take another example • Suppose we want to create a program that will read integer values and sum them up. • But we do not know exactly how many numbers the user needs to type in. • So, in our program, we are going to determine an integer value that will be considered a Sentinel and that value will be used to mark the end of the input data. • In this program, I want the user to input data from the keyboard • So, I will create an input object • static Scanner console = new Scanner(System.in); • Next, I will declare and initialize the Sentinel variable • I prefer it to be a static variable • static final int SENTINEL = 10; • public static void main(String[] args) • { • Next, I need to declare the various variables that will be used in this program • The first variable will be used to store the input numbers by the user • int number; • The second variable will hold the sum of all the numbers inputted by the user • int sum = 0; • The third variable will be the loop control variable • int counter = 0; • Next, we will write an output statement that will prompt the user to input the integer number • System.out.println( Enter consecutive number and stop at + SENTINEL); • Let’s write the input statement • number = console.nextInt(); • After, we will write the while loop statement • The loop condition will test the variable number against the variable Sentinel • while (number != SENTINEL) • { • If the condition is met • Here are the action statements to execute • The first will be an input statement that will allow the user to input the numbers • number = console.nextInt(); • The second statement will operate the sum of the numbers entered by the user • sum = sum + number; • The third statement will be used to increment the variable counter • counter++; • } • Out of the while loop • I need to write the output statement • System.out.print( The sum of all the numbers is “ + sum); • We can also add an if statement • That will allow us to print a message in case there is no input in the program • if (counter != 0) { • System.out.print( There was “ + counter + “ values”); • } • else { • System.out.println( There was no input ); • } • So, once everything is set up correctly • You can now run your program • That’s it about the Sentinel-controlled while loop, in the next video I will talk about the flag-controlled while loop • Thanks for viewing, I hope this video was informative. • Please do not forget to like and SUBSCRIBE to this channel. • Let’s meet in the next video. • #codingriver • #javatutorial • #learnjava

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