1
當我讀播放框架1.2.5的來源，我發現這個類：如何理解ApplicationClassloaderState＃hashCode的方法？
package play.classloading;
import java.util.concurrent.atomic.AtomicLong;
/**
* Each unique instance of this class represent a State of the ApplicationClassloader.
* When some classes is reloaded, them the ApplicationClassloader get a new state.
* <p/>
* This makes it easy for other parts of Play to cache stuff based on the
* the current State of the ApplicationClassloader..
* <p/>
* They can store the reference to the current state, then later, before reading from cache,
* they could check if the state of the ApplicationClassloader has changed..
*/
public class ApplicationClassloaderState {
private static AtomicLong nextStateValue = new AtomicLong();
private final long currentStateValue = nextStateValue.getAndIncrement();
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
ApplicationClassloaderState that = (ApplicationClassloaderState) o;
if (currentStateValue != that.currentStateValue) return false;
return true;
}
@Override
public int hashCode() {
return (int) (currentStateValue^(currentStateValue >>> 32));
}
}
我不瞭解hashCode方法，爲什麼用這個實現：
return (int) (currentStateValue^(currentStateValue >>> 32));