NIO到底是使用JVM的記憶體還是使用機器記憶體呢？其實，在ByteBuffer中提供了兩個申請記憶體的方法供我們選擇。
申請JVM堆記憶體：
/**
* Allocates a new byte buffer.
*
* <p> The new buffer's position will be zero, its limit will be its
* capacity, its mark will be undefined, and each of its elements will be
* initialized to zero. It will have a {@link #array backing array},
* and its {@link #arrayOffset array offset} will be zero.
*
* @param capacity
* The new buffer's capacity, in bytes
*
* @return The new byte buffer
*
* @throws IllegalArgumentException
* If the <tt>capacity</tt> is a negative integer
*/
public static ByteBuffer allocate(int capacity) {
if (capacity < 0)
throw new IllegalArgumentException();
return new HeapByteBuffer(capacity, capacity);
}
複製程式碼申請機器記憶體：
/**
* Allocates a new direct byte buffer.
*
* <p> The new buffer's position will be zero, its limit will be its
* capacity, its mark will be undefined, and each of its elements will be
* initialized to zero. Whether or not it has a
* {@link #hasArray backing array} is unspecified.
*
* @param capacity
* The new buffer's capacity, in bytes
*
* @return The new byte buffer
*
* @throws IllegalArgumentException
* If the <tt>capacity</tt> is a negative integer
*/
public static ByteBuffer allocateDirect(int capacity) {
return new DirectByteBuffer(capacity);
}
複製程式碼