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public synchronized V get(Object key) {

// 省略實現

}

public synchronized V put(K key, V value) {

// 省略實現

}

// synchronizedMap方法

public

return new SynchronizedMap<>(m);

}

// SynchronizedMap類

private static class SynchronizedMap<K,V>

implements Map<K,V>, Serializable {

private static final long serialVersionUID = 1978198479659022715L;

private final Map<K,V> m;     // Backing Map

final Object      mutex;        // Object on which to synchronize

SynchronizedMap(Map<K,V> m) {

this.m = Objects.requireNonNull(m);

mutex = this;

}

SynchronizedMap(Map<K,V> m, Object mutex) {

this.m = m;

this.mutex = mutex;

}

public int size() {

synchronized (mutex) {return m.size();}

}

public boolean isEmpty() {

synchronized (mutex) {return m.isEmpty();}

}

public boolean containsKey(Object key) {

synchronized (mutex) {return m.containsKey(key);}

}

public boolean containsValue(Object value) {

synchronized (mutex) {return m.containsValue(value);}

}

public V get(Object key) {

synchronized (mutex) {return m.get(key);}

}

public V put(K key, V value) {

synchronized (mutex) {return m.put(key, value);}

}

public V remove(Object key) {

synchronized (mutex) {return m.remove(key);}

}

// 省略其他方法

}