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Question about the task

Producer–consumer

Java Multithreading, Level 7, Lesson 9

Resolved

Not sure why it's doing that

In the TransferObject class, arrange calls to the wait/notify/notifyAll methods to ensure the sequential production and consumption of objects.
In the run methods of the ConsumerTask and ProducerTask classes, create the necessary synchronized blocks.

Expected output:

...

Put: M
Got: M
Put: N
Got: N
Put: K
Got: K
...

where M, N, and K are numbers
The main method is not tested

P.S. Always try to use a concurrent collection rather than using the wait/notify/notifyAll methods manually.
Tasks like this help you better understand the basics of how multithreaded applications work.

Requirements:

The ConsumerTask class's run method must contain a synchronized block that locks transferObject.
The ProducerTask class's run method must contain a synchronized block that locks transferObject.
The TransferObject class's get method must wait for a value to appear, and then return it once it does.
The TransferObject class's put method must wait until value is consumed, and then update its value once it is gone.
Before returning the value field, the TransferObject class's get method should set the isValuePresent flag to false and notify other threads waiting for the monitor to be released.
After updating the value field, the TransferObject class's put method should set the isValuePresent flag to true and notify other threads waiting for the monitor to be released.

package com.codegym.task.task27.task2709; /* Producer–consumer */ public class Solution { public static void main(String args[]) throws InterruptedException { TransferObject transferObject = new TransferObject(); ProducerTask producerTask = new ProducerTask(transferObject); ConsumerTask consumerTask = new ConsumerTask(transferObject); Thread.sleep(50); producerTask.stop(); consumerTask.stop(); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

15 March 2021, 15:39

solution

*hint* The put and get method should continue only if isValuePresent is, respectively, false or true.

Anthony Chalk

Level 30 , London, United Kingdom

15 March 2021, 16:19

Is the reason why it didn't work when using "value" because it isn't volatile?

Guadalupe Gagnon

Level 37 , Tampa, United States

15 March 2021, 16:31

useful

The variable 'value' never gets reset to 0, so the logic of using the if statement on value being 0 is flawed. Also the put method could set 'value' to anything within the range of an integer, including 0, as a valid value for the get method to retrieve.