Activities

My work on Java and OpenJDK, teaching, event volunteering, and other activities.

OpenJDK

I contribute fixes and improvements to Java runtime environments and related areas as an Author in OpenJDK's JDK and Valhalla projects.

OpenJDK census: dyama

Fixed Issues

  • JDK-8379818: Refactor java/nio/file/Files/StreamLinesTest.java to use JUnit (Sub-task - P4)
  • JDK-8372325: Refactor tests under jdk/java/net/httpclient to use ${test.main.class} (Bug - P4)
  • JDK-8379675: test/jdk/sun/security/pkcs11/rsa/GenKeyStore.java uses removed methods (Bug - P5)
  • JDK-8381862: Refactor remaining TestNG tests under jdk/net/ExtendedSocketOption to use JUnit (Sub-task - P4)
  • JDK-8382937: [lworld] System.arraycopy can copy null into a null-restricted array (Bug - P4)
  • JDK-8386858: [lworld] omit load_prototype_header when UseObjectMonitorTable is used (Enhancement - P4)
  • JDK-8382269: keytool man page references to "JKS" need to be cleaned up (Bug - P3)

7 other contributions

Java Ring Analysis and Revival

Since August 2025, I have been working to revive a Java Ring containing a DS1954 Java iButton. After replacing its battery, rebuilding the 1-Wire communication environment and restoring iB-IDE, we were able to run Java applets on the device again in June 2026. The project was featured on Detective! Knight Scoop on 10 July 2026.

The Java Ring Has Been Revived!

University of Tsukuba: Daisuke Yamazaki's Java Ring Project (in Japanese)

Campus Activities

Information Processing Promotion Special Committee, University of Tsukuba Student Representatives' Meeting

Activities related to information processing environments for student organizations at the University of Tsukuba.

https://www.stb.tsukuba.ac.jp/~zdk/ipc

Network Division, Information Media Systems Bureau, School Festival Executive Committee

Activities related to information infrastructure, networking, and operations for the school festival.

https://zenn.dev/p/sohosai

Teaching and Technical Events

  • 12 September 2026
    Instructor, Security Camp 2026 Mini in Aichi

    I taught a 150-minute session on how programs execute, using handwritten JVM bytecode.

  • 2025 18–19 November
    Student Staff, CODE BLUE 2025

    I helped run the international information security conference organized by BLUE, Inc. as a student staff member.

  • 15 November 2025
    On-site Staff, JJUG CCC 2025 Fall

    I helped with on-site operations at the Japan Java User Group conference.

  • 2025 18–19 October
    Tutor, Security Camp 2025 Mini Online

    I supported participants' technical learning as a tutor.

Awards

  • 2026 31 Jan–1 Feb
    Winner, Cyber Quest, Singularity Battle Quest 2025
  • 26 March 2025
    Winner, 7th CTF Kanagawa

    I led a mixed team of high school students to first place in the team CTF co-organized by Kanagawa Prefectural Police.

  • December 2024
    Kanagawa Prefectural Police Cybersecurity Headquarters Chief's Award, 9th High School Security Contest

    I received this award in the individual CTF organized by Iwasaki Gakuen, placing second by score.

Community Volunteering

Education and Memberships

  • 2026–present
    College of Information Science, School of Informatics, University of Tsukuba
  • Since November 2025
    OpenJDK Author (JDK and Valhalla)
  • Since October 2024
    Member, Japan RISS Association

Qualifications

October 2021

Information Technology Passport Examination

Other Qualifications

  • July 2025
    Network Specialist Examination
  • December 2024
    Applied Information Technology Engineer Examination
  • Registered October 2024 (expires September 2027)
    Registered Information Security Specialist
  • May 2022
    Fundamental Information Technology Engineer Examination
  • February 2022
    Oracle Certified Java Programmer, Gold SE 8
  • January 2022
    Information Security Management Examination
  • October 2021
    Oracle Certified Java Programmer, Silver SE 8

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