While loop statements - Repetition control structure - Java programming tutorial for beginners

While loop statements - Repetition control structure - Java programming tutorial for beginners Hi and welcome to this channel, In today’s video, we will start our discussion on Repetition control structures. Sometimes when writing a program you would want to repeat a set of statements a bunch of times. One way you can do that is by typing the statements in the program over and over again. This way of doing or this approach is ineffective or even impossible especially when you have huge amounts of statements to type. That’s exactly the reason why we need to learn about repetition control structures. Because they provide a simpler approach when we want to repeat a set of statements in our code. Repetition structures are also called Looping structures and in Java, there are three types of looping structures which are the while loop, the for loop, and the do … while loop. In this video, we will start discussing the while loop structure Here is the syntax of a while loop statement int score = 0; while (score less than or equal to 20) System.out.println(i + “ “); while, here is a reserved word Following, in the brackets, is the logical expression also called a loop condition or simply a condition Next, we have the action statements which is also called the body of the loop The action statements are executed only when the loop condition is met The action statement can be either a simple statement meaning that you will have only one statement Or a compound statement when you have more than one statement In case of a compound statement, you always need to surround your action statements with curly braces like this int score = 0 while (score less than or equal to 20) System.out.println(i + “ “); score = score + 5; Here is what will happen when we run this portion of code First of all, note that we have declared and initialized an integer variable score. This variable is called the Loop control variable. Next, the logical expression in the while loop statement is then evaluated. Because the condition score less than or equal to 20 evaluates to true, then the action statements in the body of the loop will execute The first action statement will output the value of score While the second action statement will increment the value of the variable score by 5 After, the logical expression in the while loop is evaluated again Because the value of the variable score is now 5 the logical expression score less than or equal to 20 will still evaluate to true and the body of the while loop will execute By outputting the values of the variable score And incrementing the value of the variable score by 5 again This process of evaluating the logical expression and executing the body of the while loop will continue until the expression score less than or equal to 20 evaluates to false That’s the reason why we are getting in the console 0 5 10 15 20 There will come a point in the loop, when the value of the variable score will become 25 But this will not be printed out Simply because, when the variable score becomes 25 the condition score than or equal to 20 evaluates to false Based on this example there are some very important point we have to note about while loops The first point to note is that you must always initialize the loop control variable, score, before you execute the loop If you remove the initialization int score = 0 Notice that the compiler is generating an error Telling us to initialize the variable The second point is that if you forget the second action statement score = score + 5 in the body of the loop You will have an infinite loop An infinite loop is a loop that continues to execute endlessly Let me remove the statement score = score + 5 And run See that our loop is executing endlessly In order to avoid an infinite loop, you always have to make sure that the loop’s body contains a statement that ensures that the condition in the while loop will eventually evaluate to false at a certain moment In our case, the statement score = score + 5 does just that The third point to note also, is that interchanging the sequence of the statements in the body of the loop may alter the result of the while loop For example, if I put the statement score = score + 5 before the output statement, like this int score = 0 while (score less than or equal to 20) score = score + 5; System.out.println(i + “ “); And run this code We will get 5 10 15 20 25 Printed in the console Typically, this is considered to be a semantic error because you would not want a condition to be true for score less than or equal to 20, and yet produce results for score greater than 20 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 #java #programming

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