What does 'synchronized' mean?
java, keyword, multithreading, synchronized
Solution
The `synchronized` keyword is all about different threads reading and writing to the same variables, objects and resources. This is not a trivial topic in Java, but here is a quote from Sun:
`synchronized` methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods.
In a very, very small nutshell: When you have two threads that are reading and writing to the same 'resource', say a variable named `foo`, you need to ensure that these threads access the variable in an atomic way. Without the `synchronized` keyword, your thread 1 may not see the change thread 2 made to `foo`, or worse, it may only be half changed. This would not be what you logically expect.
Again, this is a non-trivial topic in Java. To learn more, explore topics here on SO and the Interwebs about:
- Concurrency
- Java Memory Model
Keep exploring these topics until the name "Brian Goetz" becomes permanently associated with the term "concurrency" in your brain.
Problem
I have some questions regarding the usage and significance of the `synchronized` keyword. - What is the significance of the `synchronized` keyword? - When should methods be `synchronized`? - What does it mean programmatically and logically?