// 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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