Only create wrapper set once.

Author: Gary Gregory

src/main/java/org/apache/commons/io/input/AbstractCharacterFilterReader.java

@@ -28,7 +28,7 @@
  */
 public abstract class AbstractCharacterFilterReader extends FilterReader {
 
-    private static final IntPredicate SKIP_NONE = ch -> false;
+    protected static final IntPredicate SKIP_NONE = ch -> false;
 
     private final IntPredicate skip;
 

src/main/java/org/apache/commons/io/input/CharacterSetFilterReader.java

@@ -21,6 +21,7 @@
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.function.IntPredicate;
 
 /**
  * A filter reader that removes a given set of characters represented as {@code int} code points, handy to remove known
@@ -32,6 +33,14 @@
  */
 public class CharacterSetFilterReader extends AbstractCharacterFilterReader {
 
+    private static IntPredicate toIntPredicate(final Set<Integer> skip) {
+        if (skip == null) {
+            return SKIP_NONE;
+        }
+        final Set<Integer> unmodifiableSet = Collections.unmodifiableSet(skip);
+        return c -> unmodifiableSet.contains(Integer.valueOf(c));
+    }
+
     /**
      * Constructs a new reader.
      *
@@ -50,7 +59,7 @@ public CharacterSetFilterReader(final Reader reader, final Integer... skip) {
      * @param skip the set of characters to filter out.
      */
     public CharacterSetFilterReader(final Reader reader, final Set<Integer> skip) {
-        super(reader, c -> skip == null ? null : Collections.unmodifiableSet(skip).contains(Integer.valueOf(c)));
+        super(reader, toIntPredicate(skip));
     }
 
 }