$ java -XX:+PrintFlagsFinal -version | grep -E 'CompactStrings|CompactObjectHeaders'      (JDK 25)
     bool CompactStrings                           = true                                   {pd product} {default}
     bool UseCompactObjectHeaders                  = false                          {product lp64_product} {default}

$ java -XX:-CompactStrings -version      (JDK 25)
openjdk version "25.0.4.1" 2026-08-18 LTS
OpenJDK Runtime Environment Temurin-25.0.4.1+1 (build 25.0.4.1+1-LTS)
OpenJDK 64-Bit Server VM Temurin-25.0.4.1+1 (build 25.0.4.1+1-LTS, mixed mode)

$ java -XX:+PrintFlagsFinal -version | grep -E 'CompactStrings|CompactObjectHeaders'      (JDK 27)
     bool CompactStrings                           = true                                   {pd product} {default}
     bool UseCompactObjectHeaders                  = true                           {product lp64_product} {default}

$ java -XX:-CompactStrings -version      (JDK 27)
openjdk version "27" 2026-09-15
OpenJDK Runtime Environment Corretto-27.0.0.35.1 (build 27+35-FR)
OpenJDK 64-Bit Server VM Corretto-27.0.0.35.1 (build 27+35-FR, mixed mode)