Javadoc currently states:

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public final float CharsetEncoder.maxBytesPerChar()
Returns the maximum number of bytes that will be produced for each character of input. 
This value may be used to compute the worst-case size of the output buffer required for a given input sequence.
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This may be misinterpreted, as it may be not clear what CHARACTERs this sentence is about.
If they were Unicode code-points, UTF8Encoder.maxBytesPerChar() should return 4.0.
However, as the statement is in fact about Java characters, it correctly returns 3.0.