java

class MutablePoint {

private int x, y;

public MutablePoint() {
x = 0;
y = 0;
}

public MutablePoint(MutablePoint copy) {
this.x = copy.x;
this.y = copy.y;
}

public int getX() {
return x;
}

public void setX(int x) {
this.x = x;
}

public int getY() {
return y;
}

public void setY(int y) {
this.y = y;
}
}

/***
* don't expose the reference object  to keep thread safe
* if the entry is too many , may be is not ok.....
* @author Evan
*
*/
class MointorLocation {

private final Map<String, MutablePoint> map;

public MointorLocation(Map<String, MutablePoint> m) {

this.map = deepCopy(m);
}

public synchronized MutablePoint getLocation(String id) {

MutablePoint p = map.get(id);
//copy new MutablePoint
return p == null ? p : new MutablePoint(p);
}

public synchronized Map<String, MutablePoint> getLocations() {

//copy map
return deepCopy(map);

}

public synchronized void setLocation(String id, int x, int y) {

MutablePoint p = map.get(id);
if (p != null) {
p.setX(x);
p.setY(y);
} else {
throw new RuntimeException("id not existed");
}
}

protected Map<String, MutablePoint> deepCopy(Map<String, MutablePoint> map) {

Map<String, MutablePoint> m = new HashMap<>();
for (Map.Entry<String, MutablePoint> entry : map.entrySet()) {
m.put(entry.getKey(), new MutablePoint(entry.getValue()));
}
return m;

}

}