Update documentation

docs/pages/pmd/rules/java.md

@@ -304,7 +304,7 @@ folder: pmd/rules
 *   [ByteInstantiation](pmd_rules_java_performance.html#byteinstantiation): Calling new Byte() causes memory allocation that can be avoided by the static Byte.valueOf().It m...
 *   [ConsecutiveAppendsShouldReuse](pmd_rules_java_performance.html#consecutiveappendsshouldreuse): Consecutive calls to StringBuffer/StringBuilder .append should be chained, reusing the target obj...
 *   [ConsecutiveLiteralAppends](pmd_rules_java_performance.html#consecutiveliteralappends): Consecutively calling StringBuffer/StringBuilder.append(...) with literals should be avoided.Sinc...
-*   [InefficientEmptyStringCheck](pmd_rules_java_performance.html#inefficientemptystringcheck): String.trim().length() is an inefficient way to check if a String is really empty, as itcreates a...
+*   [InefficientEmptyStringCheck](pmd_rules_java_performance.html#inefficientemptystringcheck): String.trim().length() == 0 (or String.trim().isEmpty() for the same reason) is an inefficientway...
 *   [InefficientStringBuffering](pmd_rules_java_performance.html#inefficientstringbuffering): Avoid concatenating non-literals in a StringBuffer constructor or append() since intermediate buf...
 *   [InsufficientStringBufferDeclaration](pmd_rules_java_performance.html#insufficientstringbufferdeclaration): Failing to pre-size a StringBuffer or StringBuilder properly could cause it to re-size many times...
 *   [IntegerInstantiation](pmd_rules_java_performance.html#integerinstantiation): Calling new Integer() causes memory allocation that can be avoided by the static Integer.valueOf(...

docs/pages/pmd/rules/java/performance.md

@@ -389,12 +389,27 @@ buf.append("1m");           // good
 
 **Priority:** Medium (3)
 
-String.trim().length() is an inefficient way to check if a String is really empty, as it
-creates a new String object just to check its size. Consider creating a static function that
-loops through a string, checking Character.isWhitespace() on each character and returning
-false if a non-whitespace character is found. You can refer to Apache's StringUtils#isBlank (in commons-lang),
-Spring's StringUtils#hasText (in the Spring framework) or Google's CharMatcher#whitespace (in Guava) for
-existing implementations.
+String.trim().length() == 0 (or String.trim().isEmpty() for the same reason) is an inefficient
+way to check if a String is really blank, as it creates a new String object just to check its size.
+Consider creating a static function that loops through a string, checking Character.isWhitespace()
+on each character and returning false if a non-whitespace character is found. A Smarter code to
+check for an empty string would be:
+
+```java
+private boolean checkTrimEmpty(String str) {
+    for(int i = 0; i < str.length(); i++) {
+        if(!Character.isWhitespace(str.charAt(i))) {
+            return false;
+        }
+    }
+    return true;
+}
+```
+
+You can refer to Apache's StringUtils#isBlank (in commons-lang),
+Spring's StringUtils#hasText (in the Spring framework) or Google's
+CharMatcher#whitespace (in Guava) for existing implementations (some might
+include the check for != null).
 
 **This rule is defined by the following Java class:** [net.sourceforge.pmd.lang.java.rule.performance.InefficientEmptyStringCheckRule](https://github.com/pmd/pmd/blob/master/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/performance/InefficientEmptyStringCheckRule.java)
 
@@ -402,7 +417,7 @@ existing implementations.
 
 ``` java
 public void bar(String string) {
-    if (string != null && string.trim().size() > 0) {
+    if (string != null && string.trim().length() > 0) {
         doSomething();
     }
 }