#1134 UseStringBufferLength: false positives

[Philip Graf]

All of the following code snippets trigger a false positive for the rule UseStringBufferLength.

---

equals with empty + non-empty string:

  StringBuffer sb = new StringBuffer();
  return sb.toString().equals("" + "x");

---

trimmed string equals "":

  StringBuffer sb = new StringBuffer(" ");
  return sb.toString().trim().equals("");

---

length of trimmed string == 0:

  StringBuffer sb = new StringBuffer();
  return sb.toString().trim().length == 0;

---

equals with "" as argument of a method invocation:

 boolean bar() {
  StringBuffer sb = new StringBuffer();
  return sb.toString().equals(baz(""));
 }
 String baz(String s) {
  return s + "x";
 }

---

The code of the first three snippets is far from perfect but it should not trigger UseStringBufferLength as the snippets cannot be improved by using StringBuffer.length().

[Philip Graf]

Here's the pull request containing the fix for this bug: https://github.com/pmd/pmd/pull/23