net.sourceforge.ickles.factories.InstantFactory Maven / Gradle / Ivy

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Ickles is a suite of tiny helper classes for writing tests in Java.

There is a newer version: 0.21

/*
 * Copyright 2016 Mark Slater
 *
 * Licensed 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 net.sourceforge.ickles.factories;

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.util.Random;

public final class InstantFactory {

    private static final Random RANDOM = new Random();

    private InstantFactory() {
    }

    public static Instant anInstant() {
        return anInstantInRange(Instant.MIN, Instant.MAX);
    }

    public static Instant aLocalDateTimeCompatibleInstant() {
        return anInstantInRange(LocalDateTime.MIN.toInstant(ZoneOffset.MIN), LocalDateTime.MAX.toInstant(ZoneOffset.MAX));
    }

    public static Instant anInstantInTheLifetimeOfGenerationX() {
        return anInstantInRange(LocalDateTime.of(1965, 1, 1, 0, 0).toInstant(ZoneOffset.UTC), LocalDateTime.of(2080, 1, 1, 0, 0).toInstant(ZoneOffset.UTC));
    }

    public static Instant aComprehensibleInstant() {
        return anInstantInRange(LocalDateTime.of(-8000, 1, 1, 0, 0).toInstant(ZoneOffset.UTC), LocalDateTime.of(8000, 1, 1, 0, 0).toInstant(ZoneOffset.UTC));
    }

    private static Instant anInstantInRange(Instant min, Instant max) {
        final long EPOCH_SECONDS_RANGE = max.getEpochSecond() - min.getEpochSecond() + 1;
        long bits, seconds;
        do {
            bits = (RANDOM.nextLong() << 1) >>> 1;
            seconds = bits % EPOCH_SECONDS_RANGE;
        } while (bits - seconds + (EPOCH_SECONDS_RANGE - 1) < 0L);
        long epochSeconds = seconds + min.getEpochSecond();
        long nanos = RANDOM.nextInt(1000000000);
        return Instant.ofEpochSecond(epochSeconds, nanos);
    }
}