RFR for JDK-8022879 TEST_BUG: sun/nio/cs/MalformedSurrogates.java fails intermittently

[Eric Wang]

Hi Everyone

I am working on bug https://bugs.openjdk.java.net/browse/JDK-8022879.
The test sun/nio/cs/MalformedSurrogates.java 
<http://hg.openjdk.java.net/jdk8/tl/jdk/file/44fa6bf42846/test/sun/nio/cs/MalformedSurrogates.java> 
doesn't run if the system default encoding is UTF-8. But unfortunately, 
UTF-8 is the default charset of most test machines, it means the test 
get few chances to be executed.
Another defect is the test would failed if the default charset is UTF-16 
or UTF-32 as the test doesn't take the 2 charsets into consideration.

The idea of fix  is no matter what system charset it is, the test should 
always be executed. Here thanks Martin's suggestion that instead of 
checking byte size, we can use CharsetEncoder.canEncode() and 
CharsetEncoder.onMalformedInput(CodingErrorAction.REPLACE) to check and 
replace malformed chars.

So the test can be re-designed as below:

1. To use CharsetEncoder.canEncode() to check whether the string 
includes malformed characters.
2. If a string includes malformed characters e.g. "abc\uD800\uDB00efgh", 
then set CharsetEncoder.onMalformedInput(CodingErrorAction.REPLACE) to 
replace the malformed characters to the replacement "?" when calling 
CharsetEncoder.encode() method.
3. Verified by decoding the encoded ByteBuffer to CharBuffer, check 
whether it includes replacement "?" and compare it with old string, if 
not equal, then test passed.
4. If a sting doesn't include malformed characters e.g. 
"abc\uD800\uDC00efgh", the CharsetEncoder.encode() converts it to 
ByteBuffer which doesn't include replacement "?"
5. Verified by decoding the encoded ByteBuffer to CharBuffer, confirm 
that it doesn't include replacment "?" and compare it with old string, 
if equal, then test passed.

Please let me know if you have any comments or suggestions.

Thanks,
Eric

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