Bump Guava maximum version up to 31.0.1-jre
diff --git a/.travis.yml b/.travis.yml
index 00f7e26..89f0d1b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -34,7 +34,7 @@
     - jdk: openjdk11
       env:
         - ERRORPRONE=Y
-        - GUAVA=30.1.1-jre # ErrorProne checks for Beta APIs, so use newest supported Guava version
+        - GUAVA=31.0.1-jre # ErrorProne checks for Beta APIs, so use newest supported Guava version
       script:
         - export _JAVA_OPTIONS="-XX:GCTimeLimit=90 -XX:GCHeapFreeLimit=35"
         - ./gradlew --no-parallel --no-daemon --scan -Pguava.version=${GUAVA:-29.0-jre} -PenableErrorprone classes
@@ -43,7 +43,7 @@
         - TZ=Pacific/Chatham # flips between +12:45 and +13:45
     - jdk: openjdk15
       env:
-        - GUAVA=30.1.1-jre # newest supported Guava version
+        - GUAVA=31.0.1-jre # newest supported Guava version
 branches:
   only:
     - master
diff --git a/site/_docs/history.md b/site/_docs/history.md
index 858d40b..8b77775 100644
--- a/site/_docs/history.md
+++ b/site/_docs/history.md
@@ -33,7 +33,7 @@
 
 Compatibility: This release is tested on Linux, macOS, Microsoft Windows;
 using JDK/OpenJDK versions 8 to 15;
-Guava versions 19.0 to 30.1.1-jre;
+Guava versions 19.0 to 31.0.1-jre;
 other software versions as specified in gradle.properties.
 
 ## <a href="https://github.com/apache/calcite/releases/tag/calcite-1.27.0">1.27.0</a> / 2021-06-03