java IO文件操作入门经典例子-学会这些例子，你会发现IO是如此简单
IO是JAVASE中非常重要的一块，是面向对象的完美体现，深入学习IO，你将可以领略到很多面向对象的思想。
在公司没活干，复习了一下IO，发现很多都忘记了，所以写的不好，只够初学用。我把我复习过程中写的代码贴出来，大家共同学习，并请多指教指教哈。顺便一起讨论IO
1、文件拷贝
- Java code
try { File inputFile = new File(args[0]); if (!inputFile.exists()) { System.out.println("源文件不存在，程序终止"); System.exit(1); } File outputFile = new File(args[1]); InputStream in = new FileInputStream(inputFile); OutputStream out = new FileOutputStream(outputFile); byte date[] = new byte[1024]; int temp = 0; while ((temp = in.read(date)) != -1) { out.write(date); } in.close(); out.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }2、java读文件:实现统计某一目录下每个文件中出现的字母个数、数字个数、空格个数及行数，除此之外没有其他字符
- Java code
String fileName = "D:/date.java.bak"; // String fileName = "D:/test.qqq"; String line; int i = 0, j = 0, f = 0, k = 0; try { BufferedReader in = new BufferedReader(new FileReader(fileName)); line = in.readLine(); while (line != null) { // System.out.println(line); char c[] = line.toCharArray(); for (int i1 = 0; i1 < c.length; i1++) { // 如果是字母 if (Character.isLetter(c[i1])) i++; // 如果是数字 else if (Character.isDigit(c[i1])) j++; // 是空格 else if (Character.isWhitespace(c[i1])) f++; } line = in.readLine(); k++; } in.close(); System.out .println("字母:" + i + ",数字:" + j + ",空格:" + f + ",行数:" + k); } catch (IOException e) { e.printStackTrace(); }3、 从文件（d:\test.txt）中查出字符串”aa”出现的次数
- Java code
try { BufferedReader br = new BufferedReader(new FileReader( "D:\\test.txt")); StringBuilder sb = new StringBuilder(); while (true) { String str = br.readLine(); if (str == null) break; sb.append(str); } Pattern p = Pattern.compile("aa"); Matcher m = p.matcher(sb); int count = 0; while (m.find()) { count++; } System.out.println("\"aa\"一共出现了" + count + "次"); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); }4、 三种方法读取文件
- Java code
try { // 方法一 BufferedReader br = new BufferedReader(new FileReader(new File( "D:\\1.xls"))); // StringBuilder bd = new StringBuilder(); StringBuffer bd = new StringBuffer(); while (true) { String str = br.readLine(); if (str == null) { break; } System.out.println(str); bd.append(str); } br.close(); // System.out.println(bd.toString()); // 方法二 InputStream is = new FileInputStream(new File("d:\\1.xls")); byte b[] = new byte[Integer.parseInt(new File("d:\\1.xls").length() + "")]; is.read(b); System.out.write(b); System.out.println(); is.close(); // 方法三 Reader r = new FileReader(new File("d:\\1.xls")); char c[] = new char[(int) new File("d:\\1.xls").length()]; r.read(c); String str = new String(c); System.out.print(str); r.close(); } catch (RuntimeException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }
5、三种方法写文件
- Java code
try { PrintWriter pw = new PrintWriter(new FileWriter("d:\\1.txt")); BufferedWriter bw = new BufferedWriter(new FileWriter(new File( "d:\\1.txt"))); OutputStream os = new FileOutputStream(new File("d:\\1.txt")); // 1 os.write("ffff".getBytes()); // 2 // bw.write("ddddddddddddddddddddddddd"); // 3 // pw.print("你好sssssssssssss"); bw.close(); pw.close(); os.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }6、读取文件，并把读取的每一行存入double型数组中
- Java code
try { BufferedReader br = new BufferedReader(new FileReader(new File( "d:\\2.txt"))); StringBuffer sb = new StringBuffer(); while (true) { String str = br.readLine(); if (str == null) { break; } sb.append(str + "、"); } String str = sb.toString(); String s[] = str.split("、"); double d[] = new double[s.length]; for (int i = 0; i < s.length; i++) { d[i] = Double.parseDouble(s[i]); } for (int i = 0; i < d.length; i++) { System.out.println(d[i]); } br.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }[解决办法]
给点小意见，其实IO流还是很简单的，只要我们将流和目标文件想象成管道和水桶就很容易理解和编程了！
不知道你是否看过那些顶级大师讲IO这章的视频，给人映像很深刻！
[解决办法]
我是初学者,觉得挺适合我的。
LZ,xiexie.....
[解决办法]
import java.io.*;
public class CopyBytes{
public static void main(String[]args)throw IOException{
File inputFile=new File("farrago.txt");
File outputFile=new File("outagainb.txt");
FileInputStream in=new FileInputStream(inutFile)
FileOututStream out=new FileOutputStream(outputFile);
int c;
while((c=in.read())!=-1)
out.write(c);
in.close();
out.close();
}
}
这是我在书上抄的文件复制的代码 楼主解释下 建立 byte date[]=new byte[1024]
和 date做 in.read()的参数吗
[解决办法]
不错，支持一下。
不过 IO 最好能在 finally 中 close 哦
[解决办法]
try {
File inputFile = new File(args[0]);
if (!inputFile.exists()) {
System.out.println("源文件不存在，程序终止");
System.exit(1);
}
File outputFile = new File(args[1]);
InputStream in = new FileInputStream(inputFile);
OutputStream out = new FileOutputStream(outputFile);
byte date[] = new byte[1024];
int temp = 0;
while ((temp = in.read(date)) != -1) {
out.write(date);
}
in.close();
out.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
[解决办法]