examples/src/sort/SortAlgo.java

/*
 * Copyright 1999,2004 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 sort;

import org.apache.log4j.Logger;
import org.apache.log4j.NDC;


/**
   Example code for log4j to viewed in conjunction with the {@link
   examples.Sort Sort} class.

   <p>SortAlgo uses the bubble sort algorithm to sort an integer
   array. See also its <b><a href="doc-files/SortAlgo.java">source
   code</a></b>.

   @author Ceki G&uuml;lc&uuml; */
public class SortAlgo {
  static final String className = SortAlgo.class.getName();
  static final Logger CAT = Logger.getLogger(className);
  static final Logger OUTER = Logger.getLogger(className + ".OUTER");
  static final Logger INNER = Logger.getLogger(className + ".INNER");
  static final Logger DUMP = Logger.getLogger(className + ".DUMP");
  static final Logger SWAP = Logger.getLogger(className + ".SWAP");
  int[] intArray;

  SortAlgo(int[] intArray) {
    this.intArray = intArray;
  }

  void bubbleSort() {
    CAT.info("Entered the sort method.");

    for (int i = intArray.length - 1; i >= 0; i--) {
      NDC.push("i=" + i);
      OUTER.debug("in outer loop.");
      for (int j = 0; j < i; j++) {
        NDC.push("j=" + j);
        // It is poor practice to ship code with log staments in tight loops.
        // We do it anyway in this example.
        INNER.debug("in inner loop.");
        if (intArray[j] > intArray[j + 1]) {
          swap(j, j + 1);
        }
        NDC.pop();
      }
      NDC.pop();
    }
  }

  void dump() {
    if (!(this.intArray instanceof int[])) {
      DUMP.error("Tried to dump an uninitialized array.");
      return;
    }
    DUMP.info("Dump of integer array:");
    for (int i = 0; i < this.intArray.length; i++) {
      DUMP.info("Element [" + i + "]=" + this.intArray[i]);
    }
  }

  void swap(int l, int r) {
    // It is poor practice to ship code with log staments in tight
    // loops or code called potentially millions of times.
    SWAP.debug(
      "Swapping intArray[" + l + "]=" + intArray[l] + " and intArray[" + r
      + "]=" + intArray[r]);
    int temp = this.intArray[l];
    this.intArray[l] = this.intArray[r];
    this.intArray[r] = temp;
  }
}