Made the bulk clear() fast like bulk set() and flip() for BitSet.

classpath/java/util/BitSet.java

@@ -86,6 +86,24 @@ public class BitSet implements Serializable, Cloneable {
     }
   }
 
+  private void enlarge(int newPartition) {
+    if (bits == null || bits.length < (newPartition + 1)) {
+      long[] newBits = new long[newPartition + 1];
+      if (bits != null) {
+        System.arraycopy(bits, 0, newBits, 0, bits.length);
+      }
+      bits = newBits;
+    }
+  }
+
+  public boolean get(int index) {
+    int pos = longPosition(index);
+    if (pos < bits.length) {
+      return (bits[pos] & bitPosition(index)) != 0;
+    }
+    return false;
+  }
+
   public void flip(int index) {
     flip(index, index+1);
   }
@@ -103,31 +121,6 @@ public class BitSet implements Serializable, Cloneable {
     }
   }
 
-  private void enlarge(int newPartition) {
-    if (bits == null || bits.length < (newPartition + 1)) {
-      long[] newBits = new long[newPartition + 1];
-      if (bits != null) {
-        System.arraycopy(bits, 0, newBits, 0, bits.length);
-      }
-      bits = newBits;
-    }
-  }
-
-  public void clear(int index) {
-    int pos = longPosition(index);
-    if (pos < bits.length) {
-      bits[pos] &= (MASK ^ bitPosition(index));
-    }
-  }
-
-  public boolean get(int index) {
-    int pos = longPosition(index);
-    if (pos < bits.length) {
-      return (bits[pos] & bitPosition(index)) != 0;
-    }
-    return false;
-  }
-
   public void set(int index) {
     int pos = longPosition(index);
     enlarge(pos);
@@ -143,9 +136,18 @@ public class BitSet implements Serializable, Cloneable {
     }
   }
 
+  public void clear(int index) {
+    int pos = longPosition(index);
+    if (pos < bits.length) {
+      bits[pos] &= (MASK ^ bitPosition(index));
+    }
+  }
+
   public void clear(int start, int end) {
-    for (int i = start; i < end; i++) {
+    MaskInfoIterator iter = new MaskInfoIterator(start, end);
-      clear(i);
+    while (iter.hasNext()) {
+      MaskInfo info = iter.next();
+      bits[info.partitionIndex] &= (MASK ^ info.mask);
     }
   }
 

test/BitsetTest.java

@@ -48,6 +48,7 @@ public class BitsetTest {
     assertEquals("after 100, 102 is empty", 102, bits.nextClearBit(100));
     
     testFlip();
+    testClear();
 
     BitSet expandingSet = new BitSet();
     //should force us to have 3 partitions.
@@ -80,6 +81,23 @@ public class BitsetTest {
     assertTrue("70 should be false", !bitset.get(70));
   }
 
+  private static void testClear() {
+    BitSet bitset = new BitSet();
+    bitset.set(0, 20);
+    assertCardinality(bitset, 20);
+
+    bitset.clear(1);
+    assertTrue("bit 1 should be 0", !bitset.get(1));
+    assertCardinality(bitset, 19);
+
+    bitset.clear(0, 3);
+    assertTrue("bit 0 should be 0", !bitset.get(0));
+    assertTrue("bit 1 should be 0", !bitset.get(1));
+    assertTrue("bit 2 should be 0", !bitset.get(2));
+    assertTrue("bit 3 should be 1", bitset.get(3));
+    assertCardinality(bitset, 17);
+  }
+  
   static void assertTrue(String msg, boolean flag) {
     if (flag) {
       System.out.println(msg + " : OK.");