In programming, there are often instances where you have a repetitive task you want to execute multiple times. Loops are used to automate these repetitive tasks and allow you to create more efficient code.
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The This tutorial will discuss the basics of the The The Let\u2019s walk through an example to show how the We want to create a program that tells us how many more people can order a table before we have to put them on a waitlist. We could do so by using a Our code returns:<\/p>\n\n\n\n Let\u2019s break down our code. On the first line, we declare a variable called Our program then executes a After the increment operator has executed, our program calculates the remaining capacity of tables by subtracting \u201c Our “while” statement stops running when The The difference between The syntax for the do…while loop is as follows: Let\u2019s use an example to explain how the do…while loop works. Say that we are creating a guessing game that asks a user to guess a number between one and ten. We want our user to first be asked to enter a number before checking whether they have guessed the right number. If the user enters the wrong number, they should be promoted to try again. We could accomplish this task using a do…while loop. Here\u2019s an example of a program that asks a user to guess a number, then evaluates whether the user has guessed the correct number using a do…while loop: When we run our code, we are asked to guess the number first<\/strong>, before the condition in our Let\u2019s break down our code. First, we import the We then define two variables: one called Then, we use the Scanner method to initiate our user input. We print out the message After this code has executed, the do…while loop evaluates whether the number the user has guessed is equal to the number the user is to guess. If the user has guessed the wrong number, the contents of the Infinite loops are loops that will keep running forever. If you have a Here\u2019s an example of an infinite loop in Java: This loop will run infinitely. However, we can stop our program by using the When we run our code, the following response is returned:<\/p>\n\n\n\n In our example, the So, in our code, we use a This means that when fewer than five orders have been made, a message will be printed saying, while<\/code> and do...while<\/code> loops in Java are used to execute a block of code as long as a specific condition is met. These loops are similar to conditional if<\/code> statements, which are blocks of code that only execute if a specific condition evaluates to true. Unlike an if<\/code> statement, however, while<\/code> loops run until a condition is no longer true.
<\/p>\n\n\n\nwhile<\/code> and do...while<\/code> statements in Java, and will walk through a few examples to demonstrate these statements in a Java program.
<\/p>\n\n\n\nJava While Loop<\/h2>\n\n\n\n
while<\/code> loop loops through a block of code as long as a specified condition evaluates to true. The syntax for the while<\/code> loop is similar to that of a traditional if<\/code> statement. Here\u2019s the syntax for a Java while<\/code> loop:
<\/p>\n\n\n\nwhile (condition_is_met) {\n\t\/\/ Code to execute\n}<\/pre><\/div>\n\n\n\nwhile<\/code> loop will test the expression inside the parenthesis. If the Boolean expression evaluates to true, the body of the loop will execute, then the expression is evaluated again. The program will continue this process until the expression evaluates to false, after which point the while<\/code> loop is halted, and the rest of the program will run.
<\/p>\n\n\n\nwhile<\/code> loop can be used in Java. Say we are a carpenter and we have decided to start selling a new table in our store. We only have the capacity to make five tables, after which point people who want a table will be put on a waitlist.
<\/p>\n\n\n\nwhile<\/code> loop like this which will execute the body of the loop until the number of orders made is not less than the limit:
<\/p>\n\n\n\nint limit = 5;\nint orders_made = 0;\nwhile (orders_made < limit) {\n\torders_made++;\n\tint capacity = limit - orders_made;\n\tString message = capacity + \"more tables can be ordered.\";\n\tSystem.out.println(message);\n}<\/pre><\/div>\n\n\n\n4 more tables can be ordered.\n3 more tables can be ordered.\n2 more tables can be ordered.\n1 more tables can be ordered.\n0 more tables can be ordered.<\/pre><\/div>\n\n\n\n
limit<\/code> that keeps track of the maximum number of tables we can make. Then, we declare a variable called orders_made<\/code> that stores the number of orders made.
<\/p>\n\n\n\nwhile<\/code> loop, which runs while orders_made<\/code> is less than limit<\/code>. Then, we use the orders_made++<\/code> increment operator to add 1 to orders_made<\/code>.
<\/p>\n\n\n\norders_made<\/code> from limit<\/code>. Then, it prints out the message [capacity] more tables can be ordered.<\/code> to the console.
<\/p>\n\n\n\norders_made<\/code> is larger than limit<\/code>.
<\/p>\n\n\n\nJava Do While Loop<\/h2>\n\n\n\n
do\u2026while<\/code> loop is a type of while<\/code> loop. The do...while<\/code> loop executes the block of code in the do<\/code> block once before checking if a condition evaluates to true. Then, the program will repeat the loop as long as the condition is true.
<\/p>\n\n\n\nwhile<\/code> and do...while<\/code> loops is that while<\/code> loops evaluate a condition before<\/strong> running the code in the while<\/code> block, whereas do…while loops evaluate the condition after<\/strong> running the code in the do<\/code> block.
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<\/p>\n\n\n\ndo {\n\t\/\/ Code to execute\n} while (condition_is_met);<\/pre><\/div>\n\n\n\n
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<\/p>\n\n\n\nimport java.util.Scanner;\nclass GuessingGame {\n\tpublic static void main(String[] args) {\nint number = 8;\nint guess = 0;\nScanner input = new Scanner(System.in);\ndo {\nSystem.out.print(\"Enter a number between 1 and 10: \");\nguess = input.nextInt();\n} while (number != guess);\nSystem.out.println(\"You're correct!\");\n\t}\n}<\/pre><\/div>\n\n\n\ndo...while<\/code> loop is evaluated. Here\u2019s what happens when we try to guess a few numbers before finally guessing the correct one:<\/p>\n\n\n\nEnter a number between 1 and 10: 9\nEnter a number between 1 and 10: 1\nEnter a number between 1 and 10: 4\nEnter a number between 1 and 10: 5\nEnter a number between 1 and 10: 8\nYou're correct!<\/pre><\/div>\n\n\n\n
util.Scanner<\/code> method, which is used to collect user input. Then we define a class called GuessingGame<\/code> in which our code exists.
<\/p>\n\n\n\nnumber<\/code> which stores the number to be guessed, and another called guess<\/code> which stores the users\u2019 guess.
<\/p>\n\n\n\nEnter a number between 1 and 10:<\/code> to the console, then use the input.nextInt()<\/code> method to retrieve the number the user has entered.
<\/p>\n\n\n\ndo<\/code> loop run again; if the user has guessed the right number, the do…while loop stops executing and the message You\u2019re correct!<\/code> is printed to the console.
<\/p>\n\n\n\nInfinite Loops<\/h2>\n\n\n\n
while<\/code> loop whose statement never evaluates to false, the loop will keep going and could crash your program. So, it\u2019s important to make sure that, at some point, your while loop stops running.
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<\/p>\n\n\n\nwhile (true) {\n\t\/\/ Code to execute\n}<\/pre><\/div>\n\n\n\nbreak<\/code> statement. Let\u2019s say we are creating a program that keeps track of how many tables are in-stock. We only have five tables in stock. When there are no tables in-stock, we want our while<\/code> loop to stop. We could create a program that meets these specifications using the following code:
<\/p>\n\n\n\nBoolean tables_in_stock = true;\nint orders_made = 0;\nwhile (tables_in_stock) {\n\torders_made++;\n\tif (orders_made == 5) {\n\t\tSystem.out.println(\"We are out of stock.\");\n\t\tbreak;\n\t} else {\n\t\tint tables_left = 5 - orders_made;\n\t\tString message = \"There are \" + tables_left + \" tables in stock.\";\n\t\tSystem.out.println(message);\n\t}\n}<\/pre><\/div>\n\n\n\nThere are 4 tables in stock.\nThere are 3 tables in stock.\nThere are 2 tables in stock.\nThere are 1 tables in stock.\nWe are out of stock.<\/pre><\/div>\n\n\n\n
while<\/code> loop will continue to execute as long as tables_in_stock<\/code> is true. But we never specify a way in which tables_in_stock<\/code> can become false.
<\/p>\n\n\n\nbreak<\/code> statement that is executed when orders_made<\/code> is equal to 5.
<\/p>\n\n\n\nThere are [tables_left] tables in stock.<\/code> But when orders_made<\/code> is equal to 5, a message stating We are out of stock.<\/code> will be printed to the console, and the break statement is executed. When the break statement is run, our while<\/code> statement will stop.<\/p>\n\n\n\n