Mega Code Archive
0317 WeakHashMap
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WeakHashMap provides a Map based on weakly reachable keys. The key is removed from the map after the garbage collector clears all weak references to the key.
The following code provides a simple demonstration of the WeakHashMap class.
import java.util.Map;
import java.util.WeakHashMap;
class LargeObject {
private byte[] memory = new byte[1024 * 1024 * 50]; // 50 megabytes
}
public class Main {
public static void main(String[] args) {
Map<LargeObject, String> map = new WeakHashMap<LargeObject, String>();
LargeObject lo = new LargeObject();
map.put(lo, "Large Object");
System.out.println(map);
lo = null;
while (!map.isEmpty()) {
System.gc();
}
System.out.println(map);
}
}
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