Thinking In Java 4th Edition < iOS >

If you want to understand why Java works the way it does, it’s still an "order of magnitude" better than standard manuals.

Bruce Eckel later released "On Java 8" to address the significant changes in the language (like functional programming), though the 4th Edition remains a reference for Android developers using older Java versions. Thinking In Java 4th Edition

It might be daunting. Newer resources may be better for learning modern syntax first. If you want to understand why Java works