/**
* 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.cassandra.gms;
import java.util.BitSet;
import java.util.Random;
/**
* Implementation of a PureRandomNumber generator. Use this class cautiously. Not
* for general purpose use. Currently this is used by the Gossiper to choose a random
* endpoint to Gossip to.
*/
class PureRandom extends Random
{
private BitSet bs_ = new BitSet();
private int lastUb_;
PureRandom()
{
super();
}
public int nextInt(int ub)
{
if (ub <= 0)
throw new IllegalArgumentException("ub must be positive");
if ( lastUb_ != ub )
{
bs_.clear();
lastUb_ = ub;
}
else if(bs_.cardinality() == ub)
{
bs_.clear();
}
int value = super.nextInt(ub);
while ( bs_.get(value) )
{
value = super.nextInt(ub);
}
bs_.set(value);
return value;
}
public static void main(String[] args) throws Throwable
{
Random pr = new PureRandom();
int ubs[] = new int[] { 2, 3, 1, 10, 5, 0};
for (int ub : ubs)
{
System.out.println("UB: " + String.valueOf(ub));
for (int j = 0; j < 10; j++)
{
int junk = pr.nextInt(ub);
// Do something with junk so JVM doesn't optimize away
System.out.println(junk);
}
}
}
}