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Java / Java 21 Coding Standards Interview Questions

Why doesn't Checkstyle allow tab characters in most Java 21 style guides?

A tab character renders at a different visual width depending on the editor's tab-size setting, so a file that looks correctly indented in one developer's editor can look misaligned in another's, even though the underlying bytes are identical.

This becomes a real problem in diffs and code review: a mix of tabs and spaces in the same block can make a diff tool report a line as changed when only its whitespace representation shifted, burying the actual logic change under noise.

Standardizing on spaces (typically four per indent level) guarantees that every file renders identically everywhere - in the IDE, in a terminal, in a diff, and in a printed code review - which is why most Checkstyle configurations fail the build outright when a tab character is detected in a source file.

A key problem with tab characters in shared source code is that they:
Standardizing on spaces instead of tabs mainly guarantees:

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