java / expert
Snippet
Deterministic Off-Heap Memory with Foreign Function & Memory API
The Foreign Function & Memory (FFM) API (Java 22+) provides a safe and efficient way to access memory outside the Java heap. Unlike ByteBuffer, it uses 'Arenas' for deterministic lifecycle management, avoiding the overhead of Garbage Collection for large data sets.
snippet.java
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try (Arena arena = Arena.ofConfined()) {MemorySegment segment = arena.allocate(1024, 1);segment.setAtIndex(ValueLayout.JAVA_INT, 0, 42);int value = segment.getAtIndex(ValueLayout.JAVA_INT, 0);// Memory is released automatically when arena closes}
Breakdown
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Arena.ofConfined()
Allocates a memory arena restricted to the current thread for safety.
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arena.allocate(1024, 1)
Reserves 1024 bytes of off-heap memory with 1-byte alignment.
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segment.setAtIndex(...)
Performs a type-safe write operation into the raw memory segment.