Simple Long Id Generator : UUID GUID « Development Class « Java

1. Java
2. Development Class
3. UUID GUID

Simple Long Id Generator

     
// Copyright (c) 2003-2009, Jodd Team (jodd.org). All Rights Reserved.


/**
 * Simple synchronized sequence id generator. It generates long numbers in a
 * sequence. When counter reaches max long, it will be set back to zero.
 */
public class SimpleLongIdGenerator {

  protected volatile long value;

  protected long initialValue;
  protected long maxValue;
  protected boolean cycle;

  /**
   * Creates a new default cycled id generator. Starts from 1 and counts up to max long value.
   */
  public SimpleLongIdGenerator() {
    this(1, Long.MAX_VALUE, true);
  }

  /**
   * Creates a new cycled id generator with specified initial value.
   */
  public SimpleLongIdGenerator(long initialValue) {
    this(initialValue, Long.MAX_VALUE, true);
  }

  /**
   * Creates a new cycled id generator with specified range.
   */
  public SimpleLongIdGenerator(long initialValue, long maxValue) {
    this(initialValue, maxValue, true);
  }

  /**
   * Creates a new id generator with specified range and cycling flag.
   */
  public SimpleLongIdGenerator(long initialValue, long maxValue, boolean cycle) {
    if (initialValue < 0) {
      throw new IllegalArgumentException("Initial value '" + initialValue + "' must be a positive number.");
    }
    if (maxValue <= initialValue) {
      throw new IllegalArgumentException("Max value '" + maxValue + "' is less or equals to initial value '" + initialValue + "'.");
    }
    this.initialValue = this.value = initialValue;
    this.maxValue = maxValue;
    this.cycle = cycle;
  }

  /**
   * Returns the next value from the sequence. Thread-safe.
   */
  public synchronized long next() {
    long id = value;

    value++;
    if ((value > maxValue) || (value < 0)) {
      if (cycle == false) {
        throw new IllegalStateException("Max value already reached.");
      }
      value = initialValue;
    }
    return id;
  }
}

   
    
    
    
    
  

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