直接贴StackOverflow

https://stackoverflow.com/questions/55442531/why-do-we-ever-need-hasarray-method-in-charbuffer

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正文：

The condition for hasArray is

(hb != null) && !isReadOnly

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isReadOnly changes if you use asReadOnlyBuffer

CharBuffer.allocate(20).asReadOnlyBuffer();

for example.
So yes, we need it.

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Take this line

final CharBuffer cb = instance.getCharBuffer(...);

Is it read-only or not? Does it hold a valid char[] array? We don’t really know. If we do

cb.array();

and it is a read-only Buffer, we get a ReadOnlyBufferException.
If it isn’t backed by a char[] array we get a UnsupportedOperationException.

So what we might do is

if (cb.hasArray()) {
   final char[] arr = cb.array();
}

Now we are Exception-safe.
Also, you can be sure Oracle/OpenJDK/whateverJDK engineers know what they’re doing ;)