在Java中,上述三个类常常用于处理数据流,下面介绍一下三个类的不一样之处以及各自的用法。java
下面有三个Demo(Demo访问百度主页获取字节流而后输出)来分别说明三个类的做用:web
package 数据流;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
public class Test_InputStream {
/** * 获取字节流 * @param url * @return */
private String getStream(String url){
//获取字节流
InputStream in = null;
String result = "";
try {
in = new URL(url).openStream();
int tmp;
while((tmp = in.read()) != -1){
result += (char)tmp;
}
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//输出字节流
return result;
}
public static void main(String[] args){
String URL = "http://www.baidu.com";
Test_InputStream test = new Test_InputStream();
System.out.println(test.getStream(URL));
}
}
经过URL链接获取了InputStream流链接,而后经过read方法来一个字节一个字节的读取字节流并组合在一块儿(read方法返回-1则数据读取结束),最后以reasults返回。数组
输出以下:缓存
60 33 68 79 67 84 89 80 69 32 104 116 109 108 62 60 33 45 45 83 84 65 84 ……网络
这就是字节流,每一个数字都是一个字节(Byte,8位),因此若是读取英文的话,用字节流,而后用(char)强制转化一下就好了,但若是有中文等双字节语言或者说须要指定字符编码集的状况,就必须用到InputStreamReader将字节流转化为字符流了。svg
package 数据流;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
public class Test_InputStreamReader {
/* * 获得字符流前需先有字节流 */
private String getStream(String url){
try {
//获得字节流
InputStream in = new URL(url).openStream();
//将字节流转化成字符流,并指定字符集
InputStreamReader isr = new InputStreamReader(in,"UTF-8");
String results = "";
int tmp;
while((tmp = isr.read()) != -1){
results += (char)tmp;
}
return results;
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
/** * @param args */
public static void main(String[] args) {
// TODO Auto-generated method stub
String URL = "http://www.baidu.com";
Test_InputStreamReader test = new Test_InputStreamReader();
System.out.println(test.getStream(URL));
}
}
先获取字节流,而后建立InputStreamReader将字节流转化成字符流,并指定其字符集为UTF-8,而后使用强制转化将read到的int字节转化为char型,此时已能够输出中文字符,而且可速度上看出,输出字符流比输出字节流要快。下面是结果的部分截图:
编码
package 数据流;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
public class Test_BufferedReader {
/* * 字节流——字符流——缓存输出的字符流 */
private String getStream(String url){
try {
//获得字节流
InputStream in = new URL(url).openStream();
//将字节流转化成字符流,并指定字符集
InputStreamReader isr = new InputStreamReader(in,"UTF-8");
//将字符流以缓存的形式一行一行输出
BufferedReader bf = new BufferedReader(isr);
String results = "";
String newLine = "";
while((newLine = bf.readLine()) != null){
results += newLine+"\n";
}
return results;
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
/** * @param args */
public static void main(String[] args) {
// TODO Auto-generated method stub
String URL = "http://www.baidu.com";
Test_BufferedReader test = new Test_BufferedReader();
System.out.println(test.getStream(URL));
}
}
获取字符流后,可直接缓存,而后从缓存区取出,这时的速度比InputStreamReader又将快上不少。输出结果同上。url