Hobbyist Revives a 1990s Java Ring After Battery Failure
Hackaday Retrocomputing · July 21, 2026
curated by Sönke
Daisuke Yamazaki restored a Java Ring, a 1990s iButton wearable once handed out at Java conferences to store coffee preferences. Using a Blue Dot adapter and a downgraded 32-bit Java 1.8 runtime, he diagnosed CRC errors from a dead lithium backup battery, got help replacing it after Japanese TV coverage, and confirmed the JVM survived in ROM even though original stored data was lost.
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