Java 17 is a LTS version of Java. Java 17 should be the next version to upgrade if you are using Java 8 or Java 11. It is expected that users of Java 8 and 11 will gradually migrate to Java 17. Spring 6 is released with requirement of JDK 17+. You must upgrade to Java 17 to use Spring 6.
This book covers major changes from Java 11 to Java 17, including Java 12, 13, 14, 15, 16 and 17. Below is a list of these
RecordsSealed classesSwitch expressionsPattern matchingText blocksJFR event streaming, JVM constants API, hidden classesChanges to Java standard librariesNew garbage collectors