update gradle to version 7.6
diff --git a/lib/java/README.md b/lib/java/README.md
index 7005c60..5d9b123 100644
--- a/lib/java/README.md
+++ b/lib/java/README.md
@@ -50,13 +50,13 @@
 following this step (which is also done in the travis CI docker images):
 
 ```bash
-export GRADLE_VERSION="7.5.1"
+export GRADLE_VERSION="7.6"
 # install dependencies
 apt-get install -y --no-install-recommends openjdk-17-jdk-headless wget unzip
 # download gradle distribution
 wget https://services.gradle.org/distributions/gradle-$GRADLE_VERSION-bin.zip -q -O /tmp/gradle-$GRADLE_VERSION-bin.zip
 # check binary integrity
-echo "f6b8596b10cce501591e92f229816aa4046424f3b24d771751b06779d58c8ec4  /tmp/gradle-$GRADLE_VERSION-bin.zip" | sha256sum -c -
+echo "03c0f018d043de73187fe87d1798f4c8f494aceed1c6158b0919367926a19e4d  /tmp/gradle-$GRADLE_VERSION-bin.zip" | sha256sum -c -
 # unzip and install
 unzip -d /tmp /tmp/gradle-$GRADLE_VERSION-bin.zip
 mv /tmp/gradle-$GRADLE_VERSION /usr/local/gradle