Why does Javac reject text blocks ending with four or more " ?

[Jim Laskey]

Deepak,

It's not clear what you are commenting on.

As in your description;

        >> cat Empty.java
        public class Empty {
            public static void main(String... args) {
                String s = """

                        ""

                        """;
                System.out.println(s);
            }
        }
        >> java Empty.java

        ""

As shown in your example;

        >> cat Empty.java
        public class Empty {
            public static void main(String... args) {
                String s = """

                        """"

                        """;
                System.out.println(s);
            }
        }
        >> java Empty.java
        Empty.java:5: error: unclosed string literal
                        """"
                           ^
        Empty.java:7: error: illegal text block open delimiter sequence, missing line terminator
                        """;
                           ^
        2 errors
        error: compilation failed

If you want to include three or more quotes in a text block then escape (at least) every third quote;

        >> cat Empty.java
        public class Empty {
            public static void main(String... args) {
                String s = """

                        \"""\"

                        """;
                System.out.println(s);
            }
        }
        >> java Empty.java

        """"


Cheers.

-- Jim






> On Jul 30, 2020, at 11:04 AM, Deepak Vohra <dvohra16 at gmail.com> wrote:
> 
> Sequences of three characters are reserved for the opening and closing
> delimiter and should not occur by user code or incidentally in a text
> block. As an example, an empty string literal within a text block, while
> apparently permissible, adds three consecutive double quotes as follows:
> 
> String s ="""
> 
>                 """"
> 
>                 """;
> 
> On Thu, Jul 30, 2020 at 1:13 AM Alex Buckley <alex.buckley at oracle.com>
> wrote:
> 
>> " and "" can be used anywhere in a text block except immediately prior
>> to the closing delimiter. If a text block needs to end with " or "",
>> then the " and "" may be escaped:
>> 
>> String s1 = """
>>   ...
>>   \"""";
>> String s2 = """
>>   ...
>>   \"\"""";
>> 
>> Writing just """" or """"" runs afoul of the longstanding JLS 3.2 rule
>> about lexical translation choosing the longest possible token. That is,
>> during the process of translating characters into the TextBlock token of
>> the lexical grammar, the discovery of """ is translated as the closing
>> delimiter of TextBlock, even if a further " follows immediately.
>> 
>> Alex
>> 
>> On 7/29/2020 10:05 PM, Jayaprakash Artanareeswaran wrote:
>>> Hello,
>>> 
>>> The following code is rejected by Javac in JDK 15, although JEP 378
>> doesn't say anything about it.
>>> 
>>>     static final String TEXT_BLOCK = """
>>>               1
>>>             """"; // Notice the four quotes here?
>>> 
>>> In fact, the JEP says this:
>>> 
>>> "The use of the escape sequences \" and \n is permitted in a text block,
>> but not necessary or recommended. However, representing the sequence """ in
>> a text block requires the escaping of at least one " character, to avoid
>> mimicking the closing delimiter."
>>> 
>>> So, I would imagine it's perfectly okay for up to two consequent quotes
>> to be used anywhere in a text block.
>>> 
>>> If this is indeed backed by the spec, can the experts please point me to
>> the relevant section?
>>> Hopefully, I am asking this in the right mailing list.
>>> 
>>> Thanks,
>>> Jay
>>> 
>>