Java Reference
In-Depth Information
}
} catch (ClassNotFoundException e) {}
}
}
Example 8.4.3.6-2.
synchronized
Methods
public class Box {
private Object boxContents;
public synchronized Object get() {
Object contents = boxContents;
boxContents = null;
return contents;
}
public synchronized boolean put(Object contents) {
if (boxContents != null) return false;
boxContents = contents;
return true;
}
}
This program defines a class which is designed for concurrent use. Each instance of
the class
Box
has an instance variable
boxContents
that can hold a reference to any ob-
ject.
You can put an object in a
Box
by invoking
put
, which returns
false
if the box is already
full. You can get something out of a
Box
by invoking
get
, which returns a null refer-
ence if the box is empty.
If
put
and
get
were not
synchronized
, and two threads were executing methods for the
same instance of
Box
at the same time, then the code could misbehave. It might, for
example, lose track of an object because two invocations to put occurred at the same
time.
8.4.4. Generic Methods
These type variables are known as the
type parameters
of the method. The form of the type
parameter section of a generic method is identical to the type parameter section of a generic
