What are the default buffer size for java.io.BufferedInputStream on old and exotic JVMs?

问题

I've been doing some research for a blog post regarding java.io.BufferedInputStream and buffers. Apparently, over the years, the default has grown from a measly 512 bytes to 8192 bytes as of (presumptuously) Sun's Java 7 implementation, and was even explicitly specified in the JavaDocs in JDK 1.1.8. My question has also brought up questions of who/what deciedes what the default should be--it's not as black-n-white as I had expected.

I am curious as to what the default buffer size has been at each version release, and what it may be in other, exotic JVMs. So far I've tracked it down, via source code, JavaDocs or Sun bug reports for 1.0, 1.1, 1.4, Java 5, Java 6 and (presumptuously again) Sun's Java 7 JVM.

What I've failed to turn up is this value for

Sun JDK 1.2's JVM implementation
Sun JDK 1.3's implementation
Any other implementation's value (like IBM or something else)

So, I was wondering what those values are and where I could find a reference to them?

Or, that baring, if any SOpedians out there might have access to one of these installations. If so, could you compile and run the below code, and then report back here? Or, do you know of

import java.io.BufferedInputStream;
import java.io.InputStream;

public class BufferSizeDetector extends BufferedInputStream {
    public static void main(String[] args) {
        BufferSizeDetector bsd = new BufferSizeDetector(null);

        System.err.println(System.getProperty("java.version"));
        System.err.println(bsd.getBufferSize());
    }

    public BufferSizeDetector(InputStream in) {
        super(in);
    }

    public int getBufferSize() {
        return super.buf.length;
    }
}

回答1:

Mac OS X Tiger 10.7.0, default Apple-provided VM:

Java(TM) SE Runtime Environment (build 1.6.0_26-b03-383-11A511)
Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02-383, mixed mode)

Then:

1.6.0_26
8192

回答2:

The system:

Linux wart 2.6.33-rc1-00225-gc9f937e #2 Wed Dec 23 17:55:01 UTC 2009 armv5tel GNU/Linux
OpenJDK Runtime Environment (IcedTea6 1.4.1) (6b14-1.4.1-0ubuntu10)
OpenJDK Core VM (build 14.0-b08, interpreted mode)

The output from your program:

1.6.0_0
8192

回答3:

I'm not sure what you hope to learn from this, but since I have it in front of me... a win32 IBM 1.4.2 JRE uses a buffer size of 2048.

回答4:

Run from my IntelliJ in Windows 7:

JRE: 1.8.0_112-release-724-b6 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 7 6.1

Output:

1.8.0_121
8192

来源：https://stackoverflow.com/questions/2095269/what-are-the-default-buffer-size-for-java-io-bufferedinputstream-on-old-and-exot

标签

java

history

bufferedinputstream