/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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.apache.giraph.time;
  
  import java.util.Date;
  
  /**
   * Implementation of Time that is thread-safe and should be used in
   * production.
   */
  public class SystemTime implements Time {
    /**
     * Single instance of this object
     */
    private static final SystemTime SINGLE_TIME = new SystemTime();
  
    @Override
    public long getMilliseconds() {
      return System.currentTimeMillis();
    }
  
    @Override
    public long getMicroseconds() {
      return getNanoseconds() / NS_PER_US;
    }
  
    @Override
    public long getNanoseconds() {
      return System.nanoTime();
    }
  
    @Override
    public int getSeconds() {
      return (int) (getMilliseconds() / MS_PER_SECOND);
    }
  
    @Override
    public Date getCurrentDate() {
      return new Date();
    }
  
    @Override
    public void sleep(long milliseconds) throws InterruptedException {
      Thread.sleep(milliseconds);
    }
  
    /**
     * Get an instance (shared) of this object
     *
     * @return Instance of this object
     */
    public static Time get() {
      return SINGLE_TIME;
    }
  }