One more data-gathering exercise: I took a closer look at some popular Maven projects to see how they've evolved in their use of wrapper constructors.
----- junit:junit < 4.12 (<2014): many problems in junit.framework.Assert & org.junit.Assert 4.12-4.13 (2014-2020): a few problems in junit.framework.Assert 4.13.1 (2020): fixed org.ow2.asm:asm < 6.0 (<2017): many problems in org.objectweb.asm.ClassReader & Opcodes 6.0 (2017): problem in org.objectweb.asm.Opcodes 6.1+ (2018+): no problems commons-lang:commons-lang & org.apache.commons:commons-lang3 < 3.0 (<2011): many problems 3.0 (2011): many problems 3.1+ (2011+): fixed com.fasterxml.jackson.core:jackson-databind < 2.9.0 (<2017): one call in com.fasterxml.jackson.databind.deser.std.NumberDeserializers 2.9.0+ (2017+): fixed javax.xml.bind:jaxb-api 1.0 (2006): two problems 2.0+ (2006+): fixed Log4j (log4j:log4j & org.apache.logging.log4j:log4j-core) < 2.0 (<2014): multiple problems 2.0+ (2014+): no issues org.mockito:mockito-core < 2.1.0 (<2016): many problems, including in repackaged ASM 2.1.0+ (2016+): fixed org.scala-lang:scala-library < 2.8.0 (<2010): problems in scala.Console$, scala.Predef$, scala.mobile.Code, scala.runtime.BoxesUtility 2.8.0-2.9.3 (2010-2013): one issue, scala.actors.threadpool.locks.ReentrantReadWriteLock 2.10.0+ (2012+): fixed org.hibernate:hibernate-core < 4.0 (<2011): many, many, problems 4.0.0-5.4.22 (2011-2020): a few problems 6.0.0+ (not yet released): fixed ch.qos.logback:logback-classic < 1.0.7 (<2012): lots of problems 1.0.7+ (2012): fixed org.clojure < 1.10.0 (<2018): repackages ASM, a few other problems 1.1.0.0+ (2018+): fixed com.google.code.gson < 1.4 (<2010): problems in com.google.gson.DefaultInstanceCreators & JsonParser 1.4+ (2010+): fixed org.jetbrains.kotlin:kotlin-stdlib < 1.3.0 (<2018): no problems 1.3.0+ (2018+): new problems in kotlin.coroutines.jvm.internal.Boxing No problems: org.junit.jupiter:junit-jupiter-api (earliest release 2017) com.google.guava:guava (earliest release 2011) org.apache.commons.commons-collections4 (earliest release 2013) com.fasterxml.jackson.core:jackson-core (earliest release 2012) org.slf4j:slf4j-api (earliest release 2006) org.slf4j:slf4j-log4j12 (earliest release 2006) org.apache.logging.log4j:log4j-core (earliest release 2014) commons-io:commons-io (earliest release 2005) javax.servlet:javax.servlet-api (earliest release 2011) org.apache.httpcomponents:httpclient (earliest release 2009) ----- It does seem like the deprecation warnings introduced in 9 are working—lots of projects have responded by changing their code. A few cases worth special attention: - JUnit 4 was only very recently fixed (and it's in maintenance mode, must clients use 4.11 or 4.12, not 4.13) - Hibernate still has problems until its coming 6.0 release - Kotlin added (!) some constructor calls in 2018, and they're still there - Clojure and ASM were fixed pretty recently Still, it's a positive sign that only one of these projects is making wrapper constructor calls in its latest sources.
