被觀察者
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public class Observable<T> { List<Observer> observers = new ArrayList<Observer>(); boolean changed = false; /** * Adds the specified observer to the list of observers. If it is already * registered, it is not added a second time. * * @param observer * the Observer to add. */ public void addObserver(Observer observer) { if (observer == null) { throw new NullPointerException("observer == null"); } synchronized (this) { if (!observers.contains(observer)) observers.add(observer); } } /** * Clears the changed flag for this {@code Observable}. After calling * {@code clearChanged()}, {@code hasChanged()} will return {@code false}. */ protected void clearChanged() { changed = false; } /** * Returns the number of observers registered to this {@code Observable}. * * @return the number of observers. */ public int countObservers() { return observers.size(); } /** * Removes the specified observer from the list of observers. Passing null * won't do anything. * * @param observer * the observer to remove. */ public synchronized void deleteObserver(java.util.Observer observer) { observers.remove(observer); } /** * Removes all observers from the list of observers. */ public synchronized void deleteObservers() { observers.clear(); } /** * Returns the changed flag for this {@code Observable}. * * @return {@code true} when the changed flag for this {@code Observable} is * set, {@code false} otherwise. */ public boolean hasChanged() { return changed; } /** * If {@code hasChanged()} returns {@code true}, calls the {@code update()} * method for every observer in the list of observers using null as the * argument. Afterwards, calls {@code clearChanged()}. * <p> * Equivalent to calling {@code notifyObservers(null)}. */ public void notifyObservers() { notifyObservers(null); } /** * If {@code hasChanged()} returns {@code true}, calls the {@code update()} * method for every Observer in the list of observers using the specified * argument. Afterwards calls {@code clearChanged()}. * * @param data * the argument passed to {@code update()}. */ public void notifyObservers(T data) { int size = 0; Observer[] arrays = null; synchronized (this) { if (hasChanged()) { clearChanged(); size = observers.size(); arrays = new Observer[size]; observers.toArray(arrays); } } if (arrays != null) { for (Observer observer : arrays) { observer.update(this, data); } } } /** * Sets the changed flag for this {@code Observable}. After calling * {@code setChanged()}, {@code hasChanged()} will return {@code true}. */ protected void setChanged() { changed = true; }} |
觀察者
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public interface Observer<T> { public void update(Observable<T> observable, T data);} |
以上這篇java 在觀察者模式中使用泛型T的實例就是小編分享給大家的全部內容了，希望能給大家一個參考，也希望大家多多支持服務器之家。
