Why is synchronized used in java

The point is that the users of the code should know whether your code is thread safe or not. As a developer, you know whether your code should be thread safe or not. If not then you need to document it for the users so that they may explicitly synchronize in interesting scenarios. You need not go about synchronizing everything in your code. Synchronizing a static method in the snippet above for the functionality it provides is not correct. The users should guard against the scenario you mentioned externally wherever required.

Your static methods don't depend on any shared state, so need not be synchronized. Greg Kopff Greg Kopff Peter Lawrey Peter Lawrey k 73 73 gold badges silver badges bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready.

Java provides a way of creating threads and synchronizing their task by using synchronized blocks. Synchronized blocks in Java are marked with the synchronized keyword. A synchronized block in Java is synchronized on some object. All synchronized blocks synchronized on the same object can only have one thread executing inside them at a time. All other threads attempting to enter the synchronized block are blocked until the thread inside the synchronized block exits the block.

Only one thread can own a monitor at a given time. When a thread acquires a lock, it is said to have entered the monitor. All other threads attempting to enter the locked monitor will be suspended until the first thread exits the monitor.

Following is an example of multi threading with synchronized. In the above example, we choose to synchronize the Sender object inside the run method of the ThreadedSend class. Alternately, we could define the whole send block as synchronized and it would produce the same result. Sometimes it is preferable to synchronize only part of a method.

An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed This strategy is effective, but can present problems with liveness , as we'll see later in this lesson.

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