Synchronized and volatile

synchronized keyword , representative This method locks , Equivalent to no matter which thread （ For example, threads A）, When running to this method , Check for other threads B（ perhaps C、 D etc. ） Using this method ( Or other synchronization methods of this class )

You have to wait for it to be used synchronized Method thread B（ perhaps C 、D） Run this method before running this thread A

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We learned that synchronized It's blocking synchronization , In case of fierce thread competition, it will be upgraded to heavyweight lock .

and volatile It can be said that java The most lightweight virtual machine Synchronization mechanism

By volatile The decorated variable can ensure that each thread can get the latest value of the variable , Guarantee the data “ visibility ”. So as to avoid data dirty reading .