java打印流——Print流
只有输出流,没有输入流。
java.io
Class PrintStream
java.io
Class PrintWriter
TestPrintStream1.java
import java.io.*; /* 测试Print流1: 将把60000个字符输出到F:\\java\\io\\log.dat中, cmd窗口没有输出 */ public class TestPrintStream1 { public static void main(String[] args) { PrintStream ps = null; try { //输出文件地址 FileOutputStream fos = new FileOutputStream("F:\\java\\io\\log.dat"); //将ps指向fos ps = new PrintStream(fos); } catch (IOException e) { e.printStackTrace(); } if(ps != null){ //设置系统输出的值,从系统窗口指向ps System.setOut(ps); } int ln = 0; for(char c = 0; c <= 60000; c++){ //打印60000个unicode字符集中的字符 System.out.print(c+ " "); //每100个字符换一行 if(ln++ >=100){ System.out.println(); ln = 0; } } } }
F:\java\io>javac TestPrintStream1.java F:\java\io>java TestPrintStream1 F:\java\io>
TestPrintStream2.java
import java.io.*; /* 测试Print流2: PrintStream输出流, 在java TestPrintStream2后面接上要输出的文件 */ public class TestPrintStream2 { public static void main(String[] args) { //获取cmd中java 命令后的args数组的值 String filename = args[0]; if(filename!=null){ //filename文件名,System.out系统输出 list(filename,System.out); } } //静态方法 public static void list(String f,PrintStream fs){ try { //读取文件f,在当前目录下;br指向f BufferedReader br = new BufferedReader(new FileReader(f)); String s = null; //s=br.readLine(),通过缓冲流读取一行,赋值给s,判断s是否为null, //不为null时,通过fs(PrintStream)输出值 while((s=br.readLine())!=null){ fs.println(s); } //关闭缓冲流 br.close(); } catch (IOException e) { fs.println("无法读取文件"); } } }
F:\java\io>javac TestPrintStream2.java F:\java\io>java TestPrintStream2 TestPrintStream1.java import java.io.*; /* 测试Print流1: 将把60000个字符输出到F:\\java\\io\\log.dat中, cmd窗口没有输出 */ public class TestPrintStream1 { public static void main(String[] args) { PrintStream ps = null; try { //输出文件地址 FileOutputStream fos = new FileOutputStream("F:\\java\\io\\log.dat"); //将ps指向fos ps = new PrintStream(fos); } catch (IOException e) { e.printStackTrace(); } if(ps != null){ //设置系统输出的值,从系统窗口指向ps System.setOut(ps); } int ln = 0; for(char c = 0; c <= 60000; c++){ //打印60000个unicode字符集中的字符 System.out.print(c+ " "); //每100个字符换一行 if(ln++ >=100){ System.out.println(); ln = 0; } } } } F:\java\io>
TestPrintStream3.java
import java.util.*; import java.io.*; /* 测试Print流3: PrintWriter,输出java日志信息 */ public class TestPrintStream3 { public static void main(String[] args) { String s = null; //br指向System.in系统输入 BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); try { //写入文件F:\\java\\io\\logfile.log,true代表在其原有的值后面追加 FileWriter fw = new FileWriter("F:\\java\\io\\logfile.log", true); //Log for java(java日志) -->Log4J //log指向fw PrintWriter log = new PrintWriter(fw); while ((s = br.readLine())!=null) { if(s.equalsIgnoreCase("exit")) break; //toUpperCase将字符变为大写 System.out.println(s.toUpperCase()); //日志输出到logfile.log log.println("-----"); log.println(s.toUpperCase()); log.flush(); } log.println("==="+new Date()+"==="); log.flush(); log.close(); } catch (IOException e) { e.printStackTrace(); } } }
F:\java\io>javac TestPrintStream3.java F:\java\io>java TestPrintStream3 nihao NIHAO maomao MAOMAO 你好 你好 exit F:\java\io>java TestPrintStream3 maomao MAOMAO mimi MIMI kiki KIKI exit F:\java\io>
----- NIHAO ----- MAOMAO ----- ----- 你好 ===Wed Jul 19 22:17:50 CST 2017=== ----- MAOMAO ----- MIMI ----- KIKI ===Wed Jul 19 22:18:43 CST 2017===