generate less garbage for String substring+trim

h2/src/main/org/h2/bnf/context/DbContextRule.java

@@ -244,9 +244,9 @@ public class DbContextRule implements Rule {
         }
         String incompleteSentence = sentence.getQueryUpper();
         String incompleteFunctionName = incompleteSentence;
-        if (incompleteSentence.contains("(")) {
-            incompleteFunctionName = incompleteSentence.substring(0,
-                    incompleteSentence.indexOf('(')).trim();
+        int bracketIndex = incompleteSentence.indexOf('(');
+        if (bracketIndex != -1) {
+            incompleteFunctionName = StringUtils.trimSubstring(incompleteSentence, 0, bracketIndex);
         }
 
         // Common elements

h2/src/main/org/h2/command/Parser.java

@@ -2343,7 +2343,7 @@ public class Parser {
     }
 
     private void setSQL(Prepared command, String start, int startIndex) {
-        String sql = originalSQL.substring(startIndex, lastParseIndex).trim();
+        String sql = StringUtils.trimSubstring(originalSQL, startIndex, lastParseIndex);
         if (start != null) {
             sql = start + " " + sql;
         }

h2/src/main/org/h2/jdbc/JdbcDatabaseMetaData.java

@@ -1644,9 +1644,10 @@ public class JdbcDatabaseMetaData extends TraceObject implements
                 for (String a : array) {
                     buff.appendExceptFirst(",");
                     String f = a.trim();
-                    if (f.indexOf(' ') >= 0) {
+                    int spaceIndex = f.indexOf(' ');
+                    if (spaceIndex >= 0) {
                         // remove 'Function' from 'INSERT Function'
-                        f = f.substring(0, f.indexOf(' ')).trim();
+                        f = StringUtils.trimSubstring(f, 0, spaceIndex);
                     }
                     buff.append(f);
                 }

h2/src/main/org/h2/server/web/PageParser.java

@@ -10,6 +10,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import org.h2.util.New;
+import org.h2.util.StringUtils;
 
 /**
  * A page parser can parse an HTML page and replace the tags there.
@@ -141,7 +142,7 @@ public class PageParser {
                         setError(i);
                         return;
                     }
-                    String item = p.substring(i, j).trim();
+                    String item = StringUtils.trimSubstring(p, i, j);
                     i = j;
                     String s = (String) get(item);
                     replaceTags(s);

h2/src/main/org/h2/server/web/WebThread.java

@@ -115,7 +115,7 @@ class WebThread extends WebApp implements Runnable {
             if (begin < 0 || end < begin) {
                 file = "";
             } else {
-                file = head.substring(begin + 1, end).trim();
+                file = StringUtils.trimSubstring(head, begin + 1, end);
             }
             trace(head + ": " + file);
             file = getAllowedFile(file);

h2/src/main/org/h2/util/StringUtils.java

@@ -862,6 +862,24 @@ public class StringUtils {
         return s.substring(begin, end);
     }
 
+    /**
+     * Trim a character from a substring. Equivalence of {@code substring(begin, end).trim()}.
+     *
+     * @param s the string
+     * @param beginIndex start index of substring (inclusive)
+     * @param endIndex end index of substring (exclusive)
+     * @return trimmed substring
+     */
+    public static String trimSubstring(String s, int beginIndex, int endIndex) {
+        while (beginIndex < endIndex && s.charAt(beginIndex) <= ' ') {
+            beginIndex++;
+        }
+        while (beginIndex < endIndex && s.charAt(endIndex - 1) <= ' ') {
+            endIndex--;
+        }
+        return s.substring(beginIndex, endIndex);
+    }
+
     /**
      * Get the string from the cache if possible. If the string has not been
      * found, it is added to the cache. If there is such a string in the cache,

h2/src/test/org/h2/test/unit/TestStringUtils.java

@@ -40,6 +40,7 @@ public class TestStringUtils extends TestBase {
         testPad();
         testReplaceAll();
         testTrim();
+        testTrimSubstring();
     }
 
     private void testHex() {
@@ -252,5 +253,15 @@ public class TestStringUtils extends TestBase {
                 StringUtils.trim("zzbbzz", true, true, "z"));
     }
 
+    private void testTrimSubstring() {
+        assertEquals("", StringUtils.trimSubstring("", 0, 0));
+        assertEquals("", StringUtils.trimSubstring("    ", 0, 0));
+        assertEquals("", StringUtils.trimSubstring("    ", 4, 4));
+        assertEquals("select", StringUtils.trimSubstring(" select  from", 1, 7));
+        assertEquals("a b", StringUtils.trimSubstring(" a b ", 1, 4));
+        new AssertThrows(StringIndexOutOfBoundsException.class) { @Override
+            public void test() { StringUtils.trimSubstring(" with (", 1, 8); }
+        };
+    }
 
 }