好吧，我尝试使用下面的代码对其进行度量：
对于运行次数= 1和迭代次数= 1，URL方法大多数时候是最快的，其次是频道。我以大约十次的新鲜暂停运行。因此对于一次访问，使用URL是我想到的最快方法：
LENGTH sum: 10626, per Iteration: 10626.0CHANNEL sum: 5535, per Iteration: 5535.0URL sum: 660, per Iteration: 660.0
如果运行次数= 5，迭代次数= 50，则绘制的图片会有所不同。
LENGTH sum: 39496, per Iteration: 157.984CHANNEL sum: 74261, per Iteration: 297.044URL sum: 95534, per Iteration: 382.136
文件必须缓存对文件系统的调用，而通道和URL会有一些开销。
码：
import java.io.*;import java.net.*;import java.util.*;public enum FileSizeBench { LENGTH { @Override public long getResult() throws Exception { File me = new File(FileSizeBench.class.getResource( "FileSizeBench.class").getFile()); return me.length(); } }, CHANNEL { @Override public long getResult() throws Exception { FileInputStream fis = null; try { File me = new File(FileSizeBench.class.getResource( "FileSizeBench.class").getFile()); fis = new FileInputStream(me); return fis.getChannel().size(); } finally { fis.close(); } } }, URL { @Override public long getResult() throws Exception { InputStream stream = null; try { URL url = FileSizeBench.class .getResource("FileSizeBench.class"); stream = url.openStream(); return stream.available(); } finally { stream.close(); } } }; public abstract long getResult() throws Exception; public static void main(String[] args) throws Exception { int runs = 5; int iterations = 50; EnumMap<FileSizeBench, Long> durations = new EnumMap<FileSizeBench, Long>(FileSizeBench.class); for (int i = 0; i < runs; i++) { for (FileSizeBench test : values()) { if (!durations.containsKey(test)) { durations.put(test, 0l); } long duration = testNow(test, iterations); durations.put(test, durations.get(test) + duration); // System.out.println(test + " took: " + duration + ", per iteration: " + ((double)duration / (double)iterations)); } } for (Map.Entry<FileSizeBench, Long> entry : durations.entrySet()) { System.out.println(); System.out.println(entry.getKey() + " sum: " + entry.getValue() + ", per Iteration: " + ((double)entry.getValue() / (double)(runs * iterations))); } } private static long testNow(FileSizeBench test, int iterations) throws Exception { long result = -1; long before = System.nanoTime(); for (int i = 0; i < iterations; i++) { if (result == -1) { result = test.getResult(); //System.out.println(result); } else if ((result = test.getResult()) != result) { throw new Exception("variance detected!"); } } return (System.nanoTime() - before) / 1000; }}
