Notify,wait_ of communication between threads note using the IF

Interval printing A, B:

Note: If you use if, it causes the wait-state thread to wake up, the state change does not respond directly down the way, the duplicate print A or B may occur, and the while can be verified again; {. Wait ()}

B thread {print P} {. = P} () {. Run () () {. PRINTB () thread. ()} (Interruptedexception e)    {E.printstacktrace ()}} }}

Printing effect:

A A A A A
B-b b b b
A A A A A
B-b b b b
A A A A A
B-b b b b
A A A A A
B-b b b b
A A A A A
B-b b b b
A A A A A
B-b b b b
A A A A A
B-b b b b
A A A A A
B-b b b b
A A A A A

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Notify,wait_ of communication between threads note using the IF