Java:没有 AtomicFloat 或 AtomicDouble 吗? [英] Java: is there no AtomicFloat or AtomicDouble?

问题描述

我找到了AtomicInteger、AtomicLong，但是AtomicFloat(或AtomicDouble)在哪里?也许有什么技巧?

I have found AtomicInteger, AtomicLong, but where is AtomicFloat (or AtomicDouble)? Maybe there is some trick?

推荐答案

java.util.concurrent package 声明如下:

The API docs for the java.util.concurrent package states the following:

[...] 此外，只为那些在预期应用程序中通常有用的类型提供类.例如，没有用于表示字节的原子类.在您希望这样做的罕见情况下，您可以使用 AtomicInteger 来保存字节值，并进行适当的转换.您还可以使用 Float.floatToIntBits 和 Float.intBitstoFloat 转换保存浮点数，使用 Double.doubleToLongBits 和 Double.longBitsToDouble 转换.

[...] Additionally, classes are provided only for those types that are commonly useful in intended applications. For example, there is no atomic class for representing byte. In those infrequent cases where you would like to do so, you can use an AtomicInteger to hold byte values, and cast appropriately. You can also hold floats using Float.floatToIntBits and Float.intBitstoFloat conversions, and doubles using Double.doubleToLongBits and Double.longBitsToDouble conversions.

我并不是说这是一个方便的解决方案，但这似乎是一种解释.我想你可能想要包装一个 AtomicInteger 并为 getFloat/setFloat 等提供访问方法.

I'm not claiming it's a convenient solution, but that seems to be the explanation. I suppose you would probably want to wrap an AtomicInteger and provide access methods for getFloat / setFloat etc.

我实际上是在写一个.给你:

I actually got around writing one. Here you go:

import java.util.concurrent.atomic.AtomicInteger;
import static java.lang.Float.*;

class AtomicFloat extends Number {

    private AtomicInteger bits;

    public AtomicFloat() {
        this(0f);
    }

    public AtomicFloat(float initialValue) {
        bits = new AtomicInteger(floatToIntBits(initialValue));
    }

    public final boolean compareAndSet(float expect, float update) {
        return bits.compareAndSet(floatToIntBits(expect),
                                  floatToIntBits(update));
    }

    public final void set(float newValue) {
        bits.set(floatToIntBits(newValue));
    }

    public final float get() {
        return intBitsToFloat(bits.get());
    }

    public float floatValue() {
        return get();
    }

    public final float getAndSet(float newValue) {
        return intBitsToFloat(bits.getAndSet(floatToIntBits(newValue)));
    }

    public final boolean weakCompareAndSet(float expect, float update) {
        return bits.weakCompareAndSet(floatToIntBits(expect),
                                      floatToIntBits(update));
    }

    public double doubleValue() { return (double) floatValue(); }
    public int intValue()       { return (int) get();           }
    public long longValue()     { return (long) get();          }

}

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