[innocenat]

The Core banking system (the one that is actually processing transactions) may still be in COBOL. The other add-on services are probably in other languages. I know a few banks here (Thailand) that has successfully transition its core banking to Java, so I would guess many large banks have done the transition too. However, I doubt smaller banks would have done the transition.

[breakingcups]

Intuitively I'd feel like the larger the bank, the more work such a transition would be and thus the smaller the likelihood of it having happened.

[zhte415]

You're correct. It is a massive transition, middle-layer upon middle layer.

Oracle market a completely different code-base (which is fully Java), even single-currency code-bases, from those for larger banks, small third parties 'partners' providing implementation.

[VLM]

The larger the bank (or any company, really) the more labor they've been devoting to merger cleanup.