Utils: Add caching string split()

core/java/src/net/i2p/data/DataHelper.java

@@ -37,6 +37,8 @@ import java.util.Iterator;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Properties;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.regex.Pattern;
 import java.util.zip.Deflater;
 
 import net.i2p.I2PAppContext;
@@ -1889,4 +1891,38 @@ public class DataHelper {
         }
         return rv;
     }
+
+    /**
+     *  Same as s.split(regex) but caches the compiled pattern for speed.
+     *  This saves about 10 microseconds (Bulldozer) on subsequent invocations.
+     *
+     *  @param s non-null
+     *  @param regex non-null
+     *  @throws java.util.regex.PatternSyntaxException unchecked
+     *  @since 0.9.24
+     */
+    public static String[] split(String s, String regex) {
+        return split(s, regex, 0);
+    }
+
+    private static final ConcurrentHashMap<String, Pattern> patterns = new ConcurrentHashMap<String, Pattern>();
+
+    /**
+     *  Same as s.split(regex, limit) but caches the compiled pattern for speed.
+     *  This saves about 10 microseconds (Bulldozer) on subsequent invocations.
+     *
+     *  @param s non-null
+     *  @param regex non-null
+     *  @param limit result threshold
+     *  @throws java.util.regex.PatternSyntaxException unchecked
+     *  @since 0.9.24
+     */
+    public static String[] split(String s, String regex, int limit) {
+        Pattern p = patterns.get(regex);
+        if (p == null) {
+            p = Pattern.compile(regex);
+            patterns.putIfAbsent(regex, p);
+        }
+        return p.split(s, limit);
+    }
 }