java例程练习（打印流）

import java.util.*;
import java.io.*;

//简单的日志功能

public class Test {
public static void main(String[] args) {
String s = null;
BufferedReader br =
new BufferedReader (
new InputStreamReader(System.in));//标准输入

try {
FileWriter fw =
new FileWriter("C:/java/logfile.txt",true);

PrintWriter log = new PrintWriter(fw);
while((s = br.readLine()) != null) {
if(s.equalsIgnoreCase("exit")) break;
System.out.println(s.toUpperCase());
log.println("-----------------");
log.println(s.toUpperCase());
log.flush();
}
log.println("=========" + new Date() + "==========");
log.flush();
log.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

import java.io.*;
//改变输出流的方向

public class Test {
public static void main(String[] args) {
PrintStream ps = null;

try {
FileOutputStream fos =
new FileOutputStream("C:/java/log.txt");
ps = new PrintStream(fos);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
if(ps != null) {
System.setOut(ps);
}
int ln = 0;
for(char c = 0; c <= 60000; c++) {
System.out.print(c + " ");
if(ln++ >= 100) {
System.out.println();
ln = 0;
}
}

}
}

import java.io.*;

public class Test {
public static void main(String[] args) {
String filename = args[0];
if(filename != null) {
list(filename, System.out);//函数使用方式
}
}

public static void list(String f, PrintStream fs) {

try {
BufferedReader br =
new BufferedReader(new FileReader(f));
String s = null;
while((s = br.readLine()) != null) {
fs.println(s);
}
br.close();
} catch (IOException e) {
fs.println("无法读取文件");
}
}
}