What is the difference between volatile and synchronized?

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I've heard it all 【 heavenly ⼀ God , Underground ⼀ year 】, hypothesis CPU Of board ⾏⼀ This ordinary instruction requires ⼀ God , that CPU Reading and writing memory has to wait ⼀ Years of time .
If write ⼊ The value of the variable does not depend on the current value of the variable , Then you can ⽤ volatile
Namely x = 12 Instead of x = x+1