JAVA 右移一位比除以2快多少？

最新推荐文章于 2025-01-15 21:24:04 发布

as12cs

最新推荐文章于 2025-01-15 21:24:04 发布

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本文链接：https://blog.youkuaiyun.com/as12cs/article/details/80715592

版权

博客探讨了在JAVA中，右移一位操作与除以2在性能上的差异，通过循环测试得出几乎无明显差别的结论。

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代码：

package test2;

public class _movingright {
	public static void main(String[] args) {
		int num = -10001;
		long temp = System.nanoTime();
		System.out.println(num = num/2);
		System.out.println(System.nanoTime()-temp);
		num = -10001;
		temp = System.nanoTime();
		System.out.println(num = num>>1+1);
		System.out.println(System.nanoTime()-temp);
	}
}

运行结果

奇怪的是，写循环多次运行之后发现几乎没有差别：

package test2;

public class _movingright {
	public static void main(String[] args) {
		int times = 5000;
		long [] divide = new long [times];
		long [] moveright = new long [times];
		for (int i=0;i<times;i++) {
			int num = 10000;
			long temp = System.nanoTime();
			num = num/2;
			divide[i] = (long) (System.nanoTime()-temp);
			num = 10000;
			temp = System.nanoTime();
			num = num>>1;
			moveright[i] = (long) (System.nanoTime()-temp);
		}
		long sum1 = 0;
		long sum2 = 0;
		for (int i=0;i<times;i++) {
			sum1 += divide[i];
			sum2 += moveright[i];
		}
		double aver1 = sum1/times;
		double aver2 = sum2/times;
		System.out.println(aver1/aver2);
	}
}