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Java 25 Migration: 15 Breaking Changes That Can Break Your Production App
Most teams jumping to Java 25 are coming from 17 or 21, not from 24 — which means the breaking changes that matter are everything accumulated across that gap, not just what shipped in 25 itself. A working checklist, in the order you’re likely to hit it
Why This List Is Framed as a Gap, Not a Release
Java 25 is the next LTS after 21, and most production migrations to it skip 22, 23, and 24 entirely — they were never LTS releases most teams deployed. That means a 25 migration inherits every breaking change from three releases most teams never actually lived through, on top of whatever’s new in 25 itself. Reading only “what’s new in Java 25” and missing what changed in 22 through 24 is the single most common way this migration goes wrong. This list covers the accumulated gap.
Security and Sandbox Model
1. The Security Manager is gone. Permanently. Not deprecated — disabled
JEP 486 (JDK 24) permanently disables the Security Manager; it cannot be re-enabled by…
