code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you 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.openqa.selenium.logging;
  
  import java.util.ArrayDeque;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.logging.Handler;
  import java.util.logging.LogRecord;
  
  /**
   * A custom handler used to record log entries.
   *
   * <p>This handler queues up log records as they come, up to MAX_RECORDS (currently 1000) records.
   * If it reaches this capacity it will remove the older records from the queue before adding the
   * next one.
   */
  public class LoggingHandler extends Handler {
  
    private static final int MAX_RECORDS = 1000;
    private ArrayDeque<LogEntry> records = new ArrayDeque<>();
    private static final LoggingHandler INSTANCE = new LoggingHandler();
  
    private LoggingHandler() {}
  
    public static LoggingHandler getInstance() {
      return INSTANCE;
    }
  
    /**
     * @return an unmodifiable list of LogEntry.
     */
    public synchronized Collection<LogEntry> getRecords() {
      return Collections.unmodifiableCollection(records);
    }
  
    @Override
    public synchronized void publish(LogRecord logRecord) {
      if (isLoggable(logRecord)) {
        if (records.size() > MAX_RECORDS) {
          records.remove();
        }
        records.add(
            new LogEntry(
                logRecord.getLevel(),
                logRecord.getMillis(),
                logRecord.getLoggerName()
                    + " "
                    + logRecord.getSourceClassName()
                    + "."
                    + logRecord.getSourceMethodName()
                    + " "
                    + logRecord.getMessage()));
      }
    }
  
    @Override
    public synchronized void flush() {
      records = new ArrayDeque<>();
    }
  
    @Override
    public synchronized void close() throws SecurityException {
      records.clear();
    }
  }
  