cache and reuse DecimalFormat instances

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@1222 f203690c-595d-4dc9-a70b-905162fa7fd2

src/main/java/com/healthmarketscience/jackcess/expr/LocaleContext.java

@@ -16,6 +16,7 @@ limitations under the License.
 
 package com.healthmarketscience.jackcess.expr;
 
+import java.text.DecimalFormat;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 
@@ -50,4 +51,10 @@ public interface LocaleContext
    *         {@link EvalConfig})
    */
   public NumericConfig getNumericConfig();
+
+  /**
+   * @return an appropriately configured (i.e. DecimalFormatSymbols)
+   *         DecimalFormat for the given format.
+   */
+  public DecimalFormat createDecimalFormat(String formatStr);
 }

src/main/java/com/healthmarketscience/jackcess/impl/BaseEvalContext.java

@@ -18,6 +18,7 @@ package com.healthmarketscience.jackcess.impl;
 
 import java.io.IOException;
 import java.math.BigDecimal;
+import java.text.DecimalFormat;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.Collection;
@@ -93,6 +94,10 @@ public abstract class BaseEvalContext implements EvalContext
     return _dbCtx.getNumericConfig();
   }
 
+  public DecimalFormat createDecimalFormat(String formatStr) {
+    return _dbCtx.createDecimalFormat(formatStr);
+  }
+
   public float getRandom(Integer seed) {
     return _dbCtx.getRandom(seed);
   }

src/main/java/com/healthmarketscience/jackcess/impl/DBEvalContext.java

@@ -16,6 +16,7 @@ limitations under the License.
 
 package com.healthmarketscience.jackcess.impl;
 
+import java.text.DecimalFormat;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.Map;
@@ -41,6 +42,7 @@ public class DBEvalContext implements Expressionator.ParseContext, EvalConfig
   private final DatabaseImpl _db;
   private FunctionLookup _funcs = DefaultFunctions.LOOKUP;
   private Map<String,SimpleDateFormat> _sdfs;
+  private Map<String,DecimalFormat> _dfs;
   private TemporalConfig _temporal = TemporalConfig.US_TEMPORAL_CONFIG;
   private NumericConfig _numeric = NumericConfig.US_NUMERIC_CONFIG;
   private final RandomContext _rndCtx = new RandomContext();
@@ -103,6 +105,18 @@ public class DBEvalContext implements Expressionator.ParseContext, EvalConfig
     return sdf;
   }
 
+  public DecimalFormat createDecimalFormat(String formatStr) {
+    if(_dfs == null) {
+      _dfs = new SimpleCache<String,DecimalFormat>(MAX_CACHE_SIZE);
+    }
+    DecimalFormat df = _dfs.get(formatStr);
+    if(df == null) {
+      df = new DecimalFormat(formatStr, _numeric.getDecimalFormatSymbols());
+      _dfs.put(formatStr, df);
+    }
+    return df;
+  }
+  
   public float getRandom(Integer seed) {
     return _rndCtx.getRandom(seed);
   }

src/main/java/com/healthmarketscience/jackcess/impl/expr/DefaultFunctions.java

@@ -549,12 +549,15 @@ public class DefaultFunctions
       fmt.append("\u00A4");
     }
 
+    if(groupDigits) {
+      fmt.append("#,");
+      appendNum(fmt, '#', numGroupDigits - 1);
+    }
+    
     fmt.append(incLeadDigit ? "0" : "#");
     if(numDecDigits > 0) {
       fmt.append(".");
-      for(int i = 0; i < numDecDigits; ++i) {
-        fmt.append("0");
-      }
+      appendNum(fmt, '0', numDecDigits);
     }
 
     if(isPercent) {
@@ -569,15 +572,7 @@ public class DefaultFunctions
     }
 
     // Note, DecimalFormat rounding mode uses HALF_EVEN by default
-    DecimalFormat df = new DecimalFormat(
-        fmt.toString(), cfg.getDecimalFormatSymbols());
-    if(groupDigits) {
-      df.setGroupingUsed(true);
-      df.setGroupingSize(numGroupDigits);
-    } else {
-      df.setGroupingUsed(false);
-      df.setGroupingSize(numGroupDigits);
-    }
+    DecimalFormat df = ctx.createDecimalFormat(fmt.toString());
 
     return ValueSupport.toValue(df.format(param1.getAsBigDecimal(ctx)));
   }
@@ -602,4 +597,10 @@ public class DefaultFunctions
       throw new IllegalStateException("Duplicate function " + fname);
     }
   }
+
+  private static void appendNum(StringBuilder sb, char c, int num) {
+    for(int i = 0; i < num; ++i) {
+      sb.append(c);
+    }
+  }
 }

src/test/java/com/healthmarketscience/jackcess/impl/expr/ExpressionatorTest.java

@@ -19,6 +19,7 @@ package com.healthmarketscience.jackcess.impl.expr;
 import java.io.BufferedReader;
 import java.io.FileReader;
 import java.math.BigDecimal;
+import java.text.DecimalFormat;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.Date;
@@ -604,6 +605,11 @@ public class ExpressionatorTest extends TestCase
       return NumericConfig.US_NUMERIC_CONFIG;
     }
 
+    public DecimalFormat createDecimalFormat(String formatStr) {
+      return new DecimalFormat(
+          formatStr, NumericConfig.US_NUMERIC_CONFIG.getDecimalFormatSymbols());
+    }
+    
     public FunctionLookup getFunctionLookup() {
       return DefaultFunctions.LOOKUP;
     }