Java "Could not reserve enough space for object heap" in CI

The JVM failed to start because it could not reserve the requested heap. The -Xmx value is larger than the memory available to the process, so the VM aborts before running anything.

What this error means

A Java step fails at JVM startup with Error occurred during initialization of VM: Could not reserve enough space for ... object heap. No application output appears - the VM never initialized.

java runtime

Error occurred during initialization of VM
Could not reserve enough space for 4194304KB object heap
##[error]Process completed with exit code 1.

Common causes

-Xmx larger than available RAM

A -Xmx4g on a runner or container with less than 4 GB free cannot reserve the heap, so the JVM refuses to start.

Container memory limit below the requested heap

A cgroup memory limit smaller than -Xmx (e.g. a 2 GB container asked for a 3 GB heap) causes the reservation to fail at startup.

How to fix it

Lower -Xmx to fit the runner

Set a heap that fits within the available memory, leaving headroom for the OS.

Terminal

export MAVEN_OPTS="-Xmx1500m"
# Gradle: org.gradle.jvmargs=-Xmx1500m in gradle.properties

Let the JVM size heap to the container

Use percentage-based sizing so the heap tracks the cgroup limit instead of a fixed value.