diff --git a/src/main/org/apache/tools/ant/types/selectors/modifiedselector/ChecksumAlgorithm.java b/src/main/org/apache/tools/ant/types/selectors/modifiedselector/ChecksumAlgorithm.java
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+++ b/src/main/org/apache/tools/ant/types/selectors/modifiedselector/ChecksumAlgorithm.java
@@ -0,0 +1,148 @@
+/*
+ * Copyright  2003-2004 The Apache Software Foundation
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+
+package org.apache.tools.ant.types.selectors.modifiedselector;
+
+
+import java.util.zip.Checksum;
+import java.util.zip.CRC32;
+import java.util.zip.Adler32;
+import java.util.zip.CheckedInputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.BufferedInputStream;
+import java.security.NoSuchAlgorithmException;
+import org.apache.tools.ant.BuildException;
+
+
+/**
+ * Computes a 'checksum' for the content of file using
+ * java.util.zip.CRC32 and java.util.zip.Adler32.
+ * Use of this algorithm doesn't require any additional nested <param>s.
+ * Supported <param>s are:
+ * <table>
+ * <tr>
+ *   <th>name</th><th>values</th><th>description</th><th>required</th>
+ * </tr>
+ * <tr>
+ *   <td> algorithm.algorithm </td>
+ *   <td> ADLER | CRC ( default ) </td>
+ *   <td> name of the algorithm the checksum should use </td>
+ *   <td> no, defaults to CRC </td>
+ * </tr>
+ * </table>
+ *
+ * @version 2004-06-17
+ * @since  Ant 1.7
+ */
+public class ChecksumAlgorithm implements Algorithm {
+
+
+    // -----  member variables  -----
+
+
+    /**
+     * Checksum algorithm to be used.
+     */
+    private String algorithm = "CRC";
+
+    /**
+     * Checksum interface instance
+     */
+    private Checksum checksum = null;
+
+
+    // -----  Algorithm-Configuration  -----
+
+
+    /**
+     * Specifies the algorithm to be used to compute the checksum.
+     * Defaults to "CRC". Other popular algorithms like "ADLER" may be used as well.
+     * @param algorithm the digest algorithm to use
+     */
+    public void setAlgorithm(String algorithm) {
+        this.algorithm = algorithm;
+    }
+
+
+    /** Initialize the checksum interface. */
+    public void initChecksum() {
+        if (checksum != null) {
+            return;
+        }
+        if ("CRC".equalsIgnoreCase(algorithm)) {
+            checksum = new CRC32();
+        } else if ("ADLER".equalsIgnoreCase(algorithm)) {
+            checksum = new Adler32();
+        } else {
+            throw new BuildException(new NoSuchAlgorithmException());
+        }
+    }
+
+
+    // -----  Logic  -----
+
+
+    /**
+     * This algorithm supports only CRC and Adler.
+     * @return <i>true</i> if all is ok, otherwise <i>false</i>.
+     */
+    public boolean isValid() {
+        return "CRC".equalsIgnoreCase(algorithm) || "ADLER".equalsIgnoreCase(algorithm);
+    }
+
+
+    /**
+     * Computes a value for a file content with the specified checksum algorithm.
+     * @param file    File object for which the value should be evaluated.
+     * @return        The value for that file
+     */
+    public String getValue(File file) {
+        initChecksum();
+        String rval = null;
+
+        try {
+            if (file.canRead()) {
+                 checksum.reset();
+                 FileInputStream fis = new FileInputStream(file);
+                 CheckedInputStream check = new CheckedInputStream(fis, checksum);
+                 BufferedInputStream in = new BufferedInputStream(check);
+                 while (in.read() != -1) {
+                     // Read the file
+                 }
+                 rval = Long.toString(check.getChecksum().getValue());
+                 in.close();
+            }
+        } catch (Exception e) {
+            rval = null;
+        }
+        return rval;
+    }
+
+
+    /**
+     * Override Object.toString().
+     * @return some information about this algorithm.
+     */
+    public String toString() {
+        StringBuffer buf = new StringBuffer();
+        buf.append("<ChecksumAlgorithm:");
+        buf.append("algorithm=").append(algorithm);
+        buf.append(">");
+        return buf.toString();
+    }
+}
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