# java.lang.OutOfMemoryError: Java heap space

**Code:** `OutOfMemoryError` · **Category:** Java · **Seen on:** Java, Android

The JVM ran out of heap memory and garbage collection couldn’t free enough.

## Meaning

Either the heap (`-Xmx`) is too small for the workload, or the application leaks memory (objects stay referenced). Variants: “GC overhead limit exceeded”, “Metaspace”, “unable to create native thread”.

## Common causes

- Heap too small for the workload
- Memory leak (static collections, caches without eviction, listeners)
- Loading huge files/result sets into memory
- Container memory limit lower than JVM assumes

## Quick fix

1. Increase heap: `-Xmx2g` (or `-XX:MaxRAMPercentage=75` in containers)
2. Capture a heap dump: `-XX:+HeapDumpOnOutOfMemoryError` and analyze with Eclipse MAT
3. Stream large data instead of loading it

## Detailed fix by platform

### Java

1. In Docker/Kubernetes use `-XX:MaxRAMPercentage` so the heap respects the container limit.

### Android

1. Gradle builds: set `org.gradle.jvmargs=-Xmx4g` in gradle.properties.

## How to diagnose

1. **Variant** — Heap, Metaspace, GC overhead or native threads?
2. **Trend** — Does memory grow steadily (leak) or spike (load)?
3. **Heap dump** — Which objects dominate?

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Source: [WhatIsMyError](https://whatismyerror.com/errors/java/outofmemoryerror)