LuciferYang commented on pull request #34313:
URL: https://github.com/apache/spark/pull/34313#issuecomment-947283510
We can use the following case to test it
```
import java.util.Locale
import java.util.Formatter
val sb = new StringBuffer()
// Send all output to the Appendable object sb
val formatter = new Formatter(sb, Locale.US)
// Explicit argument indices may be used to re-order output.
formatter.format("%4$2s %3$2s %2$2s %1$2s", "a", "b", "c", "d")
assert(sb.toString == " d c b a")
sb.delete(0, sb.length())
assert(sb.toString.isEmpty)
formatter.format("%4$2s %3$2s %2$2s %0$2s", "a", "b", "c", "d")
assert(sb.toString == " d c b a")
```
This case is similar to the example written in the
https://docs.oracle.com/javase/8/docs/api/java/util/Formatter.html
The new case tests both `%4$2s %3$2s %2$2s %1$2s` and `%4$2s %3$2s %2$2s
%0$2s` and they passed when use Java 8, although "The first argument is
referenced by "1$", the second by "2$", etc." is specified in the document,
but `%0$` is not prohibited, and the result of `%0$` is equivalent to `%1$`.
The result of running the above case using Java 11 is the same as that of
Java 8.
And Exceptions are thrown only when the above case is run using Java 17
```
Illegal format argument index = 0
java.util.IllegalFormatArgumentIndexException: Illegal format argument index
= 0
at
java.base/java.util.Formatter$FormatSpecifier.index(Formatter.java:2808)
at
java.base/java.util.Formatter$FormatSpecifier.<init>(Formatter.java:2879)
at java.base/java.util.Formatter.parse(Formatter.java:2747)
at java.base/java.util.Formatter.format(Formatter.java:2671)
at java.base/java.util.Formatter.format(Formatter.java:2625)
```
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