Jonathan Schwartz, the last chief executive of Sun Microsystems, has become the first Fortune 200 boss to tweet his resignation.

Late Wednesday night, Mr. Schwartz used Twitter to publish a haiku about his exit from Oracle, which just completed its purchase of Sun last week.

“Financial crisis/Stalled too many customers/CEO no more,” Mr. Schwartz wrote.

Mr. Schwartz has been fond of using the Internet as a soapbox. At Sun, he became the first chief executive of a major company to put up his own blog. Mr. Schwartz also pushed the Securities and Exchange Commission to put blogs on equal footing with press releases and filings when it comes to disclosing critical business matters to investors.

Mr. Schwartz replaced Sun’s co-founder, Scott McNealy, as chief executive in 2006, inheriting a company that had been suffering from declining sales ever since the dot-com bust.

One of the most dramatic moves made during Mr. Schwartz’s tenure as chief executive was Sun’s decision to release the vast majority of its top software products under open-source licenses. The company hoped that broad developer interest in its software products would help attract new customers and translate into sales of other products like computer servers and storage systems.

However, Sun struggled to post consistent results and its sales continued to decline. The recession only exacerbated matters, as Sun depended on sales to many of the financial companies that were pummeled by the downturn.

I.B.M. moved to acquire Sun, only to have negotiations stall, opening the door for Oracle.

Oracle’s chief executive, Larry Ellison, is not especially fond of Mr. Schwartz. In an interview last week, Mr. Ellison said he fully expected Mr. Schwartz to resign rather than play a role in the combined company.

As for what’s next, Mr. Schwartz said in an e-mail: “In the short run, I’m planning to spend some long overdue time with my family. Longer run, with a few million businesses and a few billion consumers on the Web, rumor has it there are some interesting opportunities to be had.”