I just checked in some changes for plugins that I have been meaning to do for some time. Mainly, getting rid of the overriding of the equals() method to determing if 2 instances of a plugin are equivalent. Doing this is not so great and has implications to override hashCode(), which requires a lot more work than it was worth. There is now an isEquivalent() method in the Plugin interface that can be implemented to determine, to the degree the developer wishes, if the plugins are equivalent. The PluginRegistry uses this to determine if a plugin being started is equivalent to a plugin already running. The idea is to maintain an already running plugin over stopping it and starting the new one. This avoids losing events during the inbetween time.
Mark, I might be missing the point but you probably can simply stick your current implementation of isEquivalent() into equals.
Correctly implementing hashCode can be easy as :
public int hashCode() {
return 1; // any other constant would do as well
}another implementation which returns the same hash code for all instances of the same class.
public int hashCode() {
return this.getClass().hashCode();
}
The above is correct in the sense that it adheres to the hashCode contract.
The general contract of hashCode is (from the javadocs for Object class):
1) Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
2) If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
3) It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables.
Item 3 says that although not optional, unequal objects *may* return the same hashCode.
I hope you find the above helpful.
-Mark
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