java.lang · java.base · since Java 1.0

Runtime

declaration

public class Runtime

The JVM's runtime handle: processor count, memory figures, shutdown hooks, and process spawning (prefer ProcessBuilder).

Key methods

`static Runtime getRuntime()`	The singleton.
`int availableProcessors()`	CPUs visible to the JVM — container-quota-aware; sizes thread pools.
`long maxMemory() / totalMemory() / freeMemory()`	Heap ceiling / currently committed / free within committed.
`void addShutdownHook(Thread hook)`	Cleanup on JVM exit (not on kill -9).