java作为一种高级程序设计语言为我们屏蔽了许多与机器相关的细节，IO操作便是其中之一。java中的IO流主要分为两大类，字节流和字符流。字节流的父类是InputStream和OutputStream，继承它们的有，
ByteArrayOutputStream,
FileOutputStream,
FilterOutputStream,
ObjectOutputStream,
OutputStream,
PipedOutputStream；
AudioInputStream,
ByteArrayInputStream,
FileInputStream,
FilterInputStream,
InputStream,
ObjectInputStream,
PipedInputStream,
SequenceInputStream,
StringBufferInputStream等。
与InputStream和OutputStream相对应的类是Reader和Writer，它们下面又有
BufferedReader,
CharArrayReader,
FilterReader,
InputStreamReader,
PipedReader,
StringReader；
BufferedWriter,
CharArrayWriter,
FilterWriter,
OutputStreamWriter,
PipedWriter,
PrintWriter,
StringWriter等类继承。
java的IO流操作很好的运用了装饰者模式，下面就贴上运用IO流实现复制文件和打印文件输出的小例子。
package me.io;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Scanner;
public class Demo {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
// String commend = sc.nextLine();
System.out.println("waiting for input");
try {
handler(sc.nextLine());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void handler(String commend) throws IOException {
String[] parsed = commend.split(" ");
if ("copy".equals(parsed[0])) {
copy(parsed);
}
if ("cat".equals(parsed[0])) {
cat(parsed);
}
if ("cat2".equals(parsed[0])) {
cat2(parsed);
}
}
public static void cat2(String[] parsed) {
File file = new File(parsed[1]);
FileInputStream fis = null;
InputStreamReader isr = null;
OutputStreamWriter opw = new OutputStreamWriter(System.out);
try {
fis = new FileInputStream(file);
isr = new InputStreamReader(fis, "utf-8");
char[] temp = new char[1024];
int flag;
while (-1 != (flag = isr.read(temp))) {
opw.write(temp, 0, flag);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
try {
fis.close();
isr.close();
opw.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static void cat(String[] parsed) {
File file = new File(parsed[1]);
FileInputStream fis = null;
InputStreamReader isr = null;
try {
fis = new FileInputStream(file);
isr = new InputStreamReader(fis, "utf-8");
char[] temp = new char[1024];
int flag;
StringBuilder sb = new StringBuilder();
while (-1 != (flag = isr.read(temp))) {
sb.append(temp, 0, flag);
}
System.out.print(sb);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
try {
fis.close();
isr.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static void copy(String[] parsed) throws IOException {
File source = new File(parsed[1]);
File target = new File(parsed[2]);
FileInputStream fis = null;
FileOutputStream fos = null;
try {
fis = new FileInputStream(source);
fos = new FileOutputStream(target);
byte[] temp = new byte[1024];
int flag;
while (-1 != (flag = fis.read(temp))) {
fos.write(temp, 0, flag);
}
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (null != fis) {
fis.close();
}
if (null != fos) {
fos.close();
}
}
}
}
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