Pool (Groovy 6.0.0-alpha-1)

```
public interface Pool
extends Executor, AutoCloseable
```
A managed thread pool for parallel and concurrent operations.
Pool extends Executor so it can be used anywhere an executor is expected — including AsyncScope.withScope. It also implements AutoCloseable for use in try-with-resources blocks, ensuring clean shutdown.
Factory methods provide common pool configurations:
- virtual() — virtual-thread-per-task (JDK 21+), ideal for I/O
- fixed(int) — fixed-size thread pool with daemon threads
- cpu() — sized to availableProcessors(), for CPU-bound work
- io() — larger pool for I/O-bound or blocking operations
Inspired by GPars' PGroup pool management, modernised for virtual threads.
```
try (var pool = Pool.cpu()) {
     AsyncScope.withScope(pool, scope -> {
         scope.async(() -> cpuIntensiveWork());
         scope.async(() -> moreCpuWork());
         return null;
     );
 }
 }
```
See Also:
AsyncScope
ConcurrentConfig
Since:
6.0.0

Methods Summary

Methods
Type Params	Return Type	Name and description
	`public ForkJoinPool`	`asForkJoinPool()` Returns the underlying ForkJoinPool, if this pool is backed by one.
	`public void`	`close()` Shuts down the pool.
	`public static Pool`	`cpu()` Creates a pool sized to `Runtime.availableProcessors()`, suitable for CPU-bound work.
	`public static Pool`	`current()` Returns the pool bound to the current scope, or `null`.
	`public static Pool`	`fixed(int size)` Creates a fixed-size thread pool with daemon threads.
	`public int`	`getActiveCount()` Returns the approximate number of threads actively executing tasks.
	`public int`	`getPoolSize()` Returns the configured pool size.
	`public static Pool`	`io()` Creates a larger pool suitable for I/O-bound or blocking operations.
	`public void`	`shutdown()` Initiates an orderly shutdown.
	`public boolean`	`usesVirtualThreads()` Returns `true` if this pool uses virtual threads.
	`public static Pool`	`virtual()` Creates a virtual-thread-per-task pool (JDK 21+).
`<T>`	`public static T`	`withCurrent(Pool pool, Supplier<T> supplier)` Executes the supplier with the given pool as current, restoring the previous binding afterwards.

Inherited Methods Summary

Inherited Methods
Methods inherited from class	Name
`interface Executor`	`execute`
`interface AutoCloseable`	`close`

- Method Detail
  - public ForkJoinPool asForkJoinPool()
    
    Returns the underlying ForkJoinPool, if this pool is backed by one. Required for parallel stream isolation.
    throws:
    UnsupportedOperationException if this pool is not ForkJoinPool-backed (e.g., virtual thread pools)
    
    Returns:
    the ForkJoinPool
    Since:
    6.0.0
  - public void close()
    
    Shuts down the pool. Equivalent to shutdown().
  - public static Pool cpu()
    
    Creates a pool sized to Runtime.availableProcessors(), suitable for CPU-bound work.
    Returns:
    a new CPU pool
  - public static Pool current()
    
    Returns the pool bound to the current scope, or null.
    Set by ParallelScope.withPool using the runtime's scoped binding support.
    Returns:
    the current pool, or null if none is bound
    Since:
    6.0.0
  - public static Pool fixed(int size)
    
    Creates a fixed-size thread pool with daemon threads.
    throws:
    IllegalArgumentException if size ≤ 0
    
    Parameters:
    size - the number of threads (must be > 0)
    Returns:
    a new fixed pool
  - public int getActiveCount()
    
    Returns the approximate number of threads actively executing tasks.
  - public int getPoolSize()
    
    Returns the configured pool size. For virtual thread pools, returns Integer.MAX_VALUE.
  - public static Pool io()
    
    Creates a larger pool suitable for I/O-bound or blocking operations.
    If virtual threads are available, returns a virtual thread pool (the ideal choice for I/O). Otherwise returns a fixed pool sized to ConcurrentConfig.getDefaultParallelism.
    Returns:
    a new I/O pool
  - public void shutdown()
    
    Initiates an orderly shutdown. Previously submitted tasks are executed, but no new tasks will be accepted.
  - public boolean usesVirtualThreads()
    
    Returns true if this pool uses virtual threads.
  - public static Pool virtual()
    
    Creates a virtual-thread-per-task pool (JDK 21+).
    Each submitted task runs on its own virtual thread. This is ideal for I/O-bound workloads where tasks spend time waiting. On JDK versions that do not support virtual threads, falls back to a cached daemon thread pool.
    Returns:
    a new virtual thread pool
  - <T> public static T withCurrent(Pool pool, Supplier<T> supplier)
    
    Executes the supplier with the given pool as current, restoring the previous binding afterwards.
    Parameters:
    pool - the pool to bind
    supplier - the work to execute
    Type Parameters:
    T - the result type
    Returns:
    the supplier's result
    Since:
    6.0.0

Summary:
Method

| Detail:
Method

[Java] Interface Pool

Methods Summary

Inherited Methods Summary

Method Detail

public ForkJoinPool asForkJoinPool()

public void close()

public static Pool cpu()

public static Pool current()

public static Pool fixed(int size)

public int getActiveCount()

public int getPoolSize()

public static Pool io()

public void shutdown()

public boolean usesVirtualThreads()

public static Pool virtual()

<T> public static T withCurrent(Pool pool, Supplier<T> supplier)