Modern smartphones use high-performance processors and dedicated operating systems that can render complex PDF files effortlessly. Java-based phones, typically referred to as "feature phones" (like older Nokia S40 models, Samsung Bada devices, or generic knock-offs), have limited RAM (often less than 1MB) and slower processors.
If you are looking for Java-based libraries to build or view PDFs within an Android or modern mobile application, these are highly recommended: pdf reader for java based mobile free download
TeqTone offers a slightly more polished user interface compared to the standard Mobile PDF Reader. It attempts to render the document closer to how it looks on a desktop, though this comes at the cost of slightly higher RAM usage. Samsung Bada devices