#While loop java code

You can use a while loop to repeat the body of the loop a certain number of times as shown above. String expect = '1 2 3 4 5 6 7 8' īoolean passed = getResults(expect, output, 'Running main') Public class RunestoneTests extends CodeTestHelper

#While loop java code

Can you fix the errors? If you run an infinite loop, you may need to refresh the page to stop it (so make sure all active code windows on the page have been saved and click on Load History after refreshing). The while loop should print out the numbers 1 to 8, but it has 2 errors that cause an infinite loop and an off-by-one error. When you are tracing through code, pretend to be the computer running the code line by line, repeating the code in the loop, and keeping track of the variable values and output. Watch the following video for a tracing demo. Studies have shown that students who create tables like this do much better on code tracing problems on multiple choice exams.įigure 5: A trace table showing the values of all of the variables each time through the loop. You can create a tracing table that keeps track of the variable values each time through the loop as shown below. This would not print out anything because count = 0 at the start of the loop, so it is not greater than 10.Ī really important skill to develop is the ability to trace the values of variables and how they change during each iteration of a loop.This would not print out anything because count = 0 at the start of the loop, so it never equals 10.Notice the while statement looks a lot like an if statement, but it runs more than once. If the condition is false the first time you check it, the body of the loop will not execute. When the condition is false, we exit the loop and continue with the statements that are after the body of the while loop. If you didn’t have loops to allow you to repeat code, your programs would get very long very quickly! Using a sequence of code, selection (ifs), and repetition (loops), the control structures in programming, you can construct an algorithm to solve almost any programming problem!Ī while loop executes the body of the loop as long as (or while) a Boolean condition is true.

A loop in programming, also called iteration or repetition, is a way to repeat one or more statements. Let me try to rephrase that for newbies like me and request the experts to correct me if I am wrong.Ĭonsumer synchronized block:: synchronized (queue) block.When you play a song, you can set it to loop, which means that when it reaches the end it starts over at the beginning. Here's a web page I created a while back which explains the race condition in detail and has some sample code. Even though it was notified, it needs to be make sure the queue is for sure not empty because of this race condition. If the while loop is just an if, then when consumer #2 gets the lock after #1 and calls remove(), an exception would occur because the queue is now empty - the other consumer thread already removed the item. This means that the #1 consumer gets to go forward first to call remove() from the queue. When the item is added to the queue and notify called by the producer, #2 is moved from the wait queue to be blocked on the queue lock, but it will be behind the #1 consumer which was already blocked on the lock. When the producer locks the queue to add to it, consumer #1 may be blocked at the synchronized lock while consumer #2 is waiting on the queue. With the above code, there may be 2 consumer threads.

Certainly spurious wakeups are real and for certain architectures they are common, but race conditions are a much more likely reason for the while loop.

The primary reason why while loops are so important is race conditions between threads. Why should wait() always be called inside a loop