[alhudz]

StringSubstitutor takes the escape character from the end of a substituted value when another variable follows it directly in the template. Same issue as commons-lang StrSubstitutor, fixed in apache/commons-lang#1834.

Repro:

Map<String, String> m = Map.of("price", "5$", "x", "X", "a", "$", "b", "B");
StringSubstitutor s = new StringSubstitutor(m);
s.replace("${price}${x}"); // expected "5$X", actual "5${x}"
s.replace("${a}${b}");     // expected "$B",  actual "${b}"

After ${price} is replaced, substitute resumes scanning at the end of the inserted value, and the escape check (pos > offset && builder.charAt(pos - 1) == escapeCh) reaches back into that value. The value loses its trailing $ and ${x} is passed through unresolved.

Fix: only accept an escape character at or after the end of the last substitution, same as the commons-lang change. The class Javadoc gets the same note that was added there.

Tests are ported from commons-lang (testReplaceValueEndingWithEscape*: plain, custom delimiters, default value, empty value, variable name substitution, preserveEscapes, recursive). All 7 fail without the change and pass with it. Default mvn goal is green.

The deprecated org.apache.commons.text.StrSubstitutor has the same check (pos > offset && chars[pos - 1] == escape). I've left it alone here; happy to add it if you want it covered too.

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