Should I buffer the InputStream or the InputStreamReader?

Question

What are the differences (if any) between the following two buffering approaches?

Reader r1 = new BufferedReader(new InputStreamReader(in, "UTF-8"), bufferSize); Reader r2 = new InputStreamReader(new BufferedInputStream(in, bufferSize), "UTF-8"); 

Answer 1

r1 is more efficient. The InputStreamReader itself doesn't have a large buffer. The BufferedReader can be set to have a larger buffer than InputStreamReader. The InputStreamReader in r2 would act as a bottleneck.

In a nut: you should read the data through a funnel, not through a bottle.

---

Update: here's a little benchmark program, just copy'n'paste'n'run it. You don't need to prepare files.

package com.stackoverflow.q3459127;  import java.io.BufferedInputStream; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.File; import java.io.FileInputStream; import java.io.FileWriter; import java.io.IOException; import java.io.InputStreamReader; import java.io.Reader;  public class Test {      public static void main(String... args) throws Exception {          // Init.         int bufferSize = 10240; // 10KB.         int fileSize = 100 * 1024 * 1024; // 100MB.         File file = new File("/temp.txt");          // Create file (it's also a good JVM warmup).         System.out.print("Creating file .. ");         BufferedWriter writer = null;         try {             writer = new BufferedWriter(new FileWriter(file));             for (int i = 0; i < fileSize; i++) {                 writer.write("0");             }             System.out.printf("finished, file size: %d MB.%n", file.length() / 1024 / 1024);         } finally {             if (writer != null) try { writer.close(); } catch (IOException ignore) {}         }          // Read through funnel.         System.out.print("Reading through funnel .. ");         Reader r1 = null;                 try {             r1 = new BufferedReader(new InputStreamReader(new FileInputStream(file), "UTF-8"), bufferSize);             long st = System.nanoTime();             for (int data; (data = r1.read()) > -1;);             long et = System.nanoTime();             System.out.printf("finished in %d ms.%n", (et - st) / 1000000);         } finally {             if (r1 != null) try { r1.close(); } catch (IOException ignore) {}         }          // Read through bottle.         System.out.print("Reading through bottle .. ");         Reader r2 = null;                 try {             r2 = new InputStreamReader(new BufferedInputStream(new FileInputStream(file), bufferSize), "UTF-8");             long st = System.nanoTime();             for (int data; (data = r2.read()) > -1;);             long et = System.nanoTime();             System.out.printf("finished in %d ms.%n", (et - st) / 1000000);         } finally {             if (r2 != null) try { r2.close(); } catch (IOException ignore) {}         }          // Cleanup.         if (!file.delete()) System.err.printf("Oops, failed to delete %s. Cleanup yourself.%n", file.getAbsolutePath());     }  } 

Results at my Latitude E5500 with a Seagate Momentus 7200.3 harddisk:

 Creating file .. finished, file size: 99 MB. Reading through funnel .. finished in 1593 ms. Reading through bottle .. finished in 7760 ms.