AtomicPositiveInteger.java

/*
 * Copyright 1999-2011 Alibaba Group.
 *  
 * 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 com.alibaba.dubbo.common.utils;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * AtomicPositiveInteger
 * 
 * @author william.liangf
 * @author ding.lid
 */
public class AtomicPositiveInteger extends Number {
    
    private static final long serialVersionUID = -3038533876489105940L;
    
    private final AtomicInteger i;
    
    public AtomicPositiveInteger() {
        i = new AtomicInteger();
    }
    
    public AtomicPositiveInteger(int initialValue) {
        i = new AtomicInteger(initialValue);
    }

    public final int getAndIncrement() {
        for (;;) {
            int current = i.get();
            int next = (current >= Integer.MAX_VALUE ? 0 : current + 1);
            if (i.compareAndSet(current, next)) {
                return current;
            }
        }
    }

    public final int getAndDecrement() {
        for (;;) {
            int current = i.get();
            int next = (current <= 0 ? Integer.MAX_VALUE : current - 1);
            if (i.compareAndSet(current, next)) {
                return current;
            }
        }
    }

    public final int incrementAndGet() {
        for (;;) {
            int current = i.get();
            int next = (current >= Integer.MAX_VALUE ? 0 : current + 1);
            if (i.compareAndSet(current, next)) {
                return next;
            }
        }
    }

    public final int decrementAndGet() {
        for (;;) {
            int current = i.get();
            int next = (current <= 0 ? Integer.MAX_VALUE : current - 1);
            if (i.compareAndSet(current, next)) {
                return next;
            }
        }
    }

    public final int get() {
        return i.get();
    }

    public final void set(int newValue) {
        if (newValue < 0) {
            throw new IllegalArgumentException("new value " + newValue + " < 0");
        }
        i.set(newValue);
    }

    public final int getAndSet(int newValue) {
        if (newValue < 0) {
            throw new IllegalArgumentException("new value " + newValue + " < 0");
        }
        return i.getAndSet(newValue);
    }

    public final int getAndAdd(int delta) {
        if (delta < 0) {
            throw new IllegalArgumentException("delta " + delta + " < 0");
        }
        for (;;) {
            int current = i.get();
            int next = (current >= Integer.MAX_VALUE - delta + 1 ? delta - 1 : current + delta);
            if (i.compareAndSet(current, next)) {
                return current;
            }
        }
    }

    public final int addAndGet(int delta) {
        if (delta < 0) {
            throw new IllegalArgumentException("delta " + delta + " < 0");
        }
        for (;;) {
            int current = i.get();
            int next = (current >= Integer.MAX_VALUE - delta + 1 ? delta - 1 : current + delta);
            if (i.compareAndSet(current, next)) {
                return next;
            }
        }
    }

    public final boolean compareAndSet(int expect, int update) {
        if (update < 0) {
            throw new IllegalArgumentException("update value " + update + " < 0");
        }
        return i.compareAndSet(expect, update);
    }

    public final boolean weakCompareAndSet(int expect, int update) {
        if (update < 0) {
            throw new IllegalArgumentException("update value " + update + " < 0");
        }
        return i.weakCompareAndSet(expect, update);
    }

    public byte byteValue() {
        return i.byteValue();
    }

    public short shortValue() {
        return i.shortValue();
    }

    public int intValue() {
        return i.intValue();
    }

    public long longValue() {
        return i.longValue();
    }

    public float floatValue() {
        return i.floatValue();
    }

    public double doubleValue() {
        return i.doubleValue();
    }

    public String toString() {
        return i.toString();
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + i.hashCode();
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (!(obj instanceof AtomicPositiveInteger)) return false;
        AtomicPositiveInteger other = (AtomicPositiveInteger) obj;
        return i.intValue() == other.i.intValue();
    }

}