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Official Gyro-n Payments Java SDK

There is a newer version: 0.11.17

package jp.gopay.sdk.utils;

import java.util.Random;

public class ExponentialBackoff implements Backoff {

    final long initialIntervalMillis;
    final long maxIntervalMillis;
    final double multiplier;
    final double randomizationFactor;
    final Random random = new Random();

    double currentIntervalMillis;

    public ExponentialBackoff(long initialIntervalMillis, long maxIntervalMillis, double multiplier, double randomizationFactor) {
        if (multiplier < 1) {
            throw new IllegalArgumentException("multiplier must be >= 1");
        }
        this.maxIntervalMillis = maxIntervalMillis;
        this.multiplier = multiplier;
        this.randomizationFactor = randomizationFactor;
        this.initialIntervalMillis = initialIntervalMillis;

        currentIntervalMillis = initialIntervalMillis;
    }

    @Override
    public long next() {

        double jitter = (1 + random.nextDouble() * randomizationFactor *2) - randomizationFactor;
        long returnValue = (long)(currentIntervalMillis * Math.abs(jitter));

        calcNextInterval();

        return returnValue;
    }

    @Override
    public void reset() {
        currentIntervalMillis = initialIntervalMillis;
    }

    void calcNextInterval() {
        if (currentIntervalMillis < 1) {
            currentIntervalMillis = 1000;
        }

        if (currentIntervalMillis * multiplier >= maxIntervalMillis) {
            currentIntervalMillis = maxIntervalMillis;
        } else {
            currentIntervalMillis *= multiplier;
        }
    }
}