Suppose there is a Synchronized method which in turn calls other ordinary methods as shown below:
public static synchronized void doSomething(){
doIt1();
}
public doIt1(){
doIt2();
}
My question is, when I have the above code and call doSomething(), which is a synchronized method, will only this method be synchronized, or all the subsequent methods called, like doIt1 & doIt2, also get synchronized?
My question is, When i have above code and when I call doSomething() which is synchronized method is only this method will be synchronized or all the subsequent methods call like doIt1 & doIt2 also get synchronized ?
Only calls to doSomething() are synchronized; direct calls to doIt1() or others are not, unless those calls also use some locking of some kind.
That is, if you call doIt1(), the JVM won't look at the call sites from this method and see that "oh, there is a synchronized call site to this method so I will synchronize accesses to this method as well".
In short: the JVM ultimately assumes that you know what you are doing.
If doSomething is called, it will be synchronized from start to finish, including when it invokes doIt1 and doIt2. If doIt1 or doIt2 are invoked directly (not through doSomething), they will not be synchronized, unless the synchronized keyword is also placed on them
public static synchronized void doSomething(){
//body
}
Is identical to
static void doSomething() {
synchronized (this class) {
//body
}
}
which is identical to
static void doSomething() {
lock(this class) {
//body
} finally {
unlock();
}
}
Everything inside is synchronized because you do not release the key before body completes.
When I call doSomething() which is a synchronized method,
is only this method thread safe or all the subsequent methods
like doIt1 & doIt2 also thread safe?
Only doSomething() is thread safe because other threads can call doIt1() and doIt2().
public static synchronized void doSomething(){
doIt1();
}
public static doIt1(){
doIt2();
}
public static doIt2(){
// more code
}
synchronizedon what?