net.derquinse.common.base.LongWaterMark.java Source code

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Here is the source code for net.derquinse.common.base.LongWaterMark.java

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/*
 * Copyright (C) the original author or authors.
 *
 * 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.derquinse.common.base;

import com.google.common.base.MoreObjects;
import com.google.common.primitives.Longs;

/**
 * An long value together with its hictoric maximum and minimum values.
 * @author Andres Rodriguez
 */
public final class LongWaterMark {
    /** Current value. */
    private final long current;
    /** Maximum value. */
    private final long max;
    /** Minimum value. */
    private final long min;

    /**
     * Creates a new object with the provided initial value.
     * @param initialValue Inital value.
     * @return The created object.
     */
    public static final LongWaterMark of(long initialValue) {
        return new LongWaterMark(initialValue);
    }

    /**
     * Creates a new object with initial value 0.
     * @return The created object.
     */
    public static final LongWaterMark of() {
        return of(0);
    }

    /**
     * Constructor for an initial value.
     * @param initialValue Initial value.
     */
    private LongWaterMark(long initialValue) {
        this.current = initialValue;
        this.min = initialValue;
        this.max = initialValue;
    }

    /**
     * Constructor for a modified value.
     * @param previous Previous value.
     * @param value New current value.
     */
    private LongWaterMark(LongWaterMark previous, long value) {
        this.current = value;
        this.min = Math.min(value, previous.min);
        this.max = Math.max(value, previous.max);
    }

    /**
     * Returns the current value.
     */
    public long get() {
        return current;
    }

    /**
     * Returns the minimum value.
     */
    public long getMin() {
        return min;
    }

    /**
     * Returns the maximum value.
     */
    public long getMax() {
        return max;
    }

    /**
     * Sets the new current value.
     * @param value Value to set.
     * @return A new watermark with the provided current value.
     */
    public LongWaterMark set(long value) {
        if (current == value) {
            return this;
        }
        return new LongWaterMark(this, value);
    }

    /**
     * Adds a certain amount to the current value.
     * @param value Value to add.
     * @return A new watermark with the modified value.
     */
    public LongWaterMark add(long value) {
        return set(current + value);
    }

    /**
     * Adds one to the current value.
     * @return A new watermark with the modified value.
     */
    public LongWaterMark inc() {
        return add(1);
    }

    /**
     * Subtract one to the current value.
     * @return A new watermark with the modified value.
     */
    public LongWaterMark dec() {
        return add(-1);
    }

    public int hashCode() {
        return ((527 + Longs.hashCode(current)) * 31 + Longs.hashCode(min)) * 31 + Longs.hashCode(max);
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj instanceof LongWaterMark) {
            LongWaterMark m = (LongWaterMark) obj;
            return current == m.current && min == m.min && max == m.max;
        }
        return false;
    }

    @Override
    public String toString() {
        return MoreObjects.toStringHelper(this).add("current", current).add("min", min).add("max", max).toString();
    }

}