Predicate that matches the opposite of its argument

src/main/java/com/greplin/lucene/predicate/Predicates.java

@@ -4,7 +4,11 @@
 
 package com.greplin.lucene.predicate;
 
+import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.search.BooleanClause;
+import org.apache.lucene.util.Bits;
+
+import java.io.IOException;
 
 /**
  * Common predicates.
@@ -46,4 +50,79 @@ public static BitsProvider or(final BitsProvider... bitsProviders) {
     return result;
   }
 
+
+  /**
+   * Creates a new predicate bits provider that matches documents
+   * not matched by the argument.
+   * @param bitsProvider the predicate to negate.
+   * @return a new predicate bits provider that matches documents
+   * not matched by the argument.
+   */
+  public static BitsProvider not(final BitsProvider bitsProvider) {
+    return new InverseBitsProvider(bitsProvider);
+  }
+
+
+  /**
+   * BitsProvider that matches the opposite set of bits as its
+   * argument.
+   */
+  private static final class InverseBitsProvider extends BitsProvider {
+
+    /**
+     * The original bits to negate.
+     */
+    private final BitsProvider original;
+
+
+    /**
+     * Creates a BitsProvider that negates its argument.
+     * @param original the bits to negate.
+     */
+    private InverseBitsProvider(final BitsProvider original) {
+      this.original = original;
+    }
+
+
+    @Override
+    public Bits get(final IndexReader reader) throws IOException {
+      return new InverseBits(this.original.get(reader));
+    }
+
+  }
+
+
+  /**
+   * Bits that matches the opposite set of bits as its argument.
+   */
+  private static final class InverseBits implements Bits {
+
+    /**
+     * The original bits to negate.
+     */
+    private final Bits original;
+
+
+    /**
+     * Creates Bits that negate the argument.
+     * @param original the bits to negate.
+     */
+    private InverseBits(final Bits original) {
+      this.original = original;
+    }
+
+
+    @Override
+    public boolean get(final int index) {
+      return !this.original.get(index);
+    }
+
+
+    @Override
+    public int length() {
+      return this.original.length();
+    }
+
+  }
+
 }