I/O

含有InputStream和OutputStream的都是字節流

含有read和write的都是字符流

 

《摘自Java編程思想》

import java.io.*;
public class IOStreamDemo {
// Throw exceptions to console:
public static void main(String[] args)throws IOException {
// 1. Reading input by lines:
BufferedReader in =new BufferedReader(new FileReader("IOStreamDemo.java"));
String s, s2 = new String();
while((s = in.readLine())!= null)
s2 += s + "/n";
in.close();
// 1b. Reading standard input:
BufferedReader stdin =new BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter a line:");
System.out.println(stdin.readLine());

// 2. Input from memory
StringReader in2 = new StringReader(s2);
int c;
while((c = in2.read()) != -1)
System.out.print((char)c);

// 3. Formatted memory input
try {
DataInputStream in3 =new DataInputStream(new ByteArrayInputStream(s2.getBytes()));
while(true)
System.out.print((char)in3.readByte());
} catch(EOFException e) {
System.err.println("End of stream");
}

// 4. File output
try {
BufferedReader in4 =new BufferedReader(new StringReader(s2));
PrintWriter out1 =new PrintWriter(new BufferedWriter(new FileWriter("IODemo.out")));
int lineCount = 1;
while((s = in4.readLine()) != null )
out1.println(lineCount++ + ": " + s);
out1.close();
} catch(EOFException e) {
System.err.println("End of stream");
}

// 5. Storing & recovering data
try {
DataOutputStream out2 =new DataOutputStream(new    BufferedOutputStream(new FileOutputStream("Data.txt")));
out2.writeDouble(3.14159);
out2.writeChars("That was pi/n");
out2.writeBytes("That was pi/n");
out2.close();
DataInputStream in5 =new DataInputStream(new BufferedInputStream(new FileInputStream("Data.txt")));
BufferedReader in5br =new BufferedReader(new InputStreamReader(in5));
// Must use DataInputStream for data:
System.out.println(in5.readDouble());

// Can now use the "proper" readLine():
System.out.println(in5br.readLine());
// But the line comes out funny.
// The one created with writeBytes is OK:
System.out.println(in5br.readLine());
} catch(EOFException e) {
System.err.println("End of stream");
}

// 6. Reading/writing random access files
RandomAccessFile rf =new RandomAccessFile("rtest.dat", "rw");
for(int i = 0; i < 10; i++)
rf.writeDouble(i*1.414);
rf.close();
rf =
new RandomAccessFile("rtest.dat", "rw");
rf.seek(5*8);
rf.writeDouble(47.0001);
rf.close();
rf =
new RandomAccessFile("rtest.dat", "r");
for(int i = 0; i < 10; i++)
System.out.println(
"Value " + i + ": " +
rf.readDouble());
rf.close();
}
} ///:~