How to remove small lines created within the merged polygon using JTS

Question

I am using UnaryOp.union method provided by JTS library to merge a group of geomery objects into a single geometry object. However after merging the polygon, there are small lines visible within the polygon and I am looking for some thoughts on how to remove all those small lines? Here is the screenshot

Group of Polygons:

Merged Polygon with small lines within the polygon:

Code snippet:

UnaryUnionOp.union(jtsGeometries);