使用缓存字节数组读取java字节流时，第一次读取是，读满缓存字节数组大小，才进行下次读取，还是随机读一个小于数组大小的值，再进行下次读取？？？

读取本地文件时，首次读取读满整个字节数组，在进行下次读取。

package com.lyf.test;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import org.junit.Test;

public class ReadFile {

@Test

public void readTxt() {

InputStream is = null;

String path = this.getClass().getClassLoader().getResource("abc.txt")

.getPath();

System.out.println(path);

String content = "";

String loopContentString ="";

try {

is = new FileInputStream(path);

byte buff[] = new byte[16];

int len = is.read(buff);

content = new String(buff, 0, len);

System.out.println(len);

while (len != -1) {

len = is.read(buff);

System.out.println(len);

if(len != -1){

content += new String(buff,0,len);

}

}

System.out.println(content);

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}finally{

try {

is.close();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

}

结果：其中abc.txt 大小就26个字节

读取远程数据接口数据流时，

String queryUrl = "https://www.kuaidi100.com/chaxun?com=yuantong&nu=887240223128139035";

try {

URL url = new URL(queryUrl);

URLConnection con = url.openConnection();

con.setAllowUserInteraction(false);

urlStream= url.openStream();

String type = con.guessContentTypeFromStream(urlStream);

String charSet = null;

if (type == null){

type = con.getContentType();

}

if (type == null || type.trim().length() == 0

|| type.trim().indexOf("text/html") < 0){

return;

}

if (type.indexOf("charset=") > 0){

charSet = type.substring(type.indexOf("charset=") + 8);

}

byte b[] = new byte[100];

int numRead = urlStream.read(b);

String content = new String(b, 0, numRead);

System.out.println("b中的内容用ascii表示,第3个字符的码是="+b[2]+"||第一次:"+numRead+"||"+content);

int i = 0;

while (numRead != -1) {

numRead = urlStream.read(b);

if (numRead != -1) {

i++;

// String newContent = new String(b, 0, numRead);

String newContent = new String(b, 0, numRead, charSet);

System.out.println("第"+i+"次:"+numRead+"||"+newContent);

content += newContent;

}

}

System.out.println(content);

} catch (MalformedURLException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}finally{

try {

urlStream.close();

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

读取结果：远程数据流的大小2032个字节

第一次读取只读了，27个字节，

问题：为啥读取本地文件和远程数据的首次读取不同，是网络问题，还是java中read函数的限制？？

纳闷............