debugging-interview - GrindLoop: Android & iOS Interview Prep

String.format Locale Bug: Why “1234,50” Throws NumberFormatException on Android

October 9, 2026 by Arsam

Calculator on euro banknotes, illustrating a String.format locale bug in an Android checkout amount

A String.format locale bug turns 1234.50 into 1234,50 or Arabic digits, so toDouble() throws NumberFormatException. Runnable repro, fix and interview answer.

Why viewModelScope.launch(SupervisorJob()) Still Crashes Your App

September 29, 2026 by Arsam

Orange balloon drifting away with its string hanging loose, representing a coroutine detached from viewModelScope by launch(SupervisorJob())

Passing SupervisorJob() to launch in viewModelScope doesn’t stop a crash, and it detaches the coroutine from onCleared(). Here’s the two-bug reason, a runnable repro, the fix, and the interview answer.

Found the Bug in Your Android Debugging Interview and Still Didn’t Pass?

September 28, 2026 by Hass

Laptop showing a code editor next to a mobile emulator, the setup for an Android debugging interview

In an Android debugging interview, the first green test is often only the midpoint. What the bug squash round scores, and the traps that sink candidates who find the bug.