What is a lock in a synchronized method ??

Question

Greetings,
I have a synchronized reset method whose job is to reset every variable i am using in that class.. its a synchronized method so when i am doing the reset stuff, no other method in that class can update that variable. But someone told me i need to also put lock inside the reset method and check for the lock everywhere where i update those variables ( So that variable doesn't update itself and lose its value as reset would be resetting that variable.) How do i lock all these variables in that reset method and how do i check for the lock where i would be updating that variable.
Example: Psedo code
class {
int a =0;
int b = 0;
method update {
a = 5;
method update1{
b = 6;
synchronized method reset{
a =0;
b = 0;

Answer 1

javanewbie83 wrote:
Greetings,
I have a synchronized reset method whose job is to reset every variable i am using in that class.. its a synchronized method so when i am doing the reset stuff, no other method in that class can update that variable. But someone told me i need to also put lock inside the reset method and check for the lock everywhere where i update those variables ( So that variable doesn't update itself and lose its value as reset would be resetting that variable.) How do i lock all these variables in that reset method and how do i check for the lock where i would be updating that variable.You don't need to "check" for the lock. When you have a synchronized block or method, the synhcronized keyword tells the VM to stop executing that thread until it can attain the object's lock, then give the object's lock to that thread, and then take it back when the thread leaves the synchronized block (or calls wait()). It's all automatic.
Note that you'll need to synchronize not only write access to the variable(s) in question, but read access also, in order to ensure that reader threads see the values written by writers.