code: private void merge(final GeometryFunction callback) {
  		GeometryOperationService operationService = new GeometryOperationServiceImpl();
  		UnionInfo unionInfo = new UnionInfo();
  		unionInfo.setUsePrecisionAsBuffer(true);
  		unionInfo.setPrecision(precision);
  		operationService.union(geometries, unionInfo, new Callback<Geometry, Throwable>() {
  
  			public void onSuccess(Geometry result) {
  				callback.execute(result);
  			}
  
  			public void onFailure(Throwable reason) {
  				reason.printStackTrace();
  			}
  		});
  	}
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