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java读写文件代码 java文件
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用java读取桌面上的文档"abc.txt",程序怎么写?
给一个代码你就知道了,代码里面文件的路径改成你电脑上的文件的路径
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
/**
* file IO流读取并输出文件
* @author Administrator
*
*/
public class FileIO {
public static void main(String[] args) throws IOException {
FileInputStream fis = new FileInputStream("src/day03/BrDemo.java");// 要读的文件路径
InputStreamReader isr = new InputStreamReader(fis);// 字符流
BufferedReader br = new BufferedReader(isr); // 缓冲
String line = null;
while ((line = br.readLine()) != null) {// 字符不等于空
System.out.println(line);// 一行一行地输出
}
br.close();// 关闭文件
}
}
java文件读写
在网上查了很多关于修改文件的方法,不得其要领。自己想了两个取巧的办法,来解决对文件的修改。一:读取一个文件file1(FileReader and BufferedReader),进行操作后写入file2(FileWriter and BufferedWriter),然后删除file1,更改file2文件名为file1(Rename()方法)。二:创建字符缓冲流(StringBuffer),读取文件内容赋给字符缓冲流,再将字符缓冲流中的内容写入到读取的文件中。例如: test.txt 这里是放在d盘的根目录下,内容如下 able adj 有才干的,能干的 active adj 主动的,活跃的 adaptable adj 适应性强的 adroit adj 灵巧的,机敏的 运行结果生成在同目录的 test1.txt中 able #adj*有才干的,能干的 active #adj*主动的,活跃的 adaptable #adj*适应性强的 adroit #adj*灵巧的,机敏的 代码: public class Test { public static void main(String[] args) throws Exception{ BufferedReader br = new BufferedReader(new FileReader("D:\\test.txt")); StringBuffer sb = new StringBuffer(); String lineContent = null ;while( (lineContent = br.readLine()) != null){ String[] sp = lineContent.split(" ");sp[0] = sp[0].concat(" *");sp[1] = sp[1].concat("# ");for(int i=0;i sb.append(sp[i]);}sb.append("\r\n");}FileWriter fw = new FileWriter("D:\\test2.txt"); fw.write(sb.toString()); br.close(); fw.close(); }}
java读取文本文件代码
java读取文本文件java读写文件代码的方法有很多 这个例子主要介绍最简单 最常用java读写文件代码的BufferedReader类 完整例子如下 package net chinaunix blog hzm text;import java io BufferedReader;import java io FileReader;import java io IOException;public class ReadFile {private String path;public ReadFile(String filePath){path = filePath;}public String[] openFile() throws IOException{FileReader fr = new FileReader(path) BufferedReader textReader = new BufferedReader(fr) String[] textData = new String[readLines()];int i;for(i= ; i readLines() i++){textData[i] = textReader readLine() }textReader close() return textData;}int readLines() throws IOException{FileReader fileToRead = new FileReader(path) BufferedReader bf = new BufferedReader(fileToRead) int numberOfLines = ;@SuppressWarnings( unused )String oneLine;while((oneLine = bf readLine()) != null){numberOfLines++;}bf close() return numberOfLines;}}package net chinaunix blog hzm text;import java io IOException;public class FileData {public static void main(String[] args) throws IOException{String filePath = C:/text txt ;try{ReadFile reader = new ReadFile(filePath) String[] content = reader openFile() int i;for(i= ;icontent length;i++){System out println(content[i]) }}catch(IOException e){System out println( 异常信息 + e getMessage()) }}}java io BufferedReaderThe buffer size may be specified or the default size may be used The default is large enough for most purposes In general each read request made of a Reader causes a corresponding read request to be made of the underlying character or byte stream It is therefore advisable to wrap a BufferedReader around any Reader whose read() operations may be costly such as FileReaders and InputStreamReaders For example BufferedReader in = new BufferedReader(new FileReader( foo in )) will buffer the input from the specified file Without buffering each invocation of read() or readLine() could cause bytes to be read from the file converted into characters and then returned which can be very inefficient Programs that use DataInputStreams for textual input can be localized by replacing each DataInputStream with an appropriate BufferedReader java io FileReaderFileReader is meant for reading streams of characters For reading streams of raw bytes consider using a FileInputStream lishixinzhi/Article/program/Java/hx/201311/26249
java读取、修改、写入txt文件
模拟java读写文件代码:先创建一个TXT文件(内容来自控制台)java读写文件代码;然后读取文件并在控制台输出;最后实现对新创建的TXT文件(的数据进行排序后)的复制。分别对应三个函数,调用顺序需要注意:创建、读取、复制。
效果图如下:绿色部分为控制台输入的内容(当输入end时,结束)
代码如下:
package com.baidu;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Arrays;
import java.util.Scanner;
import java.util.Vector;
public class CreateAndReadTxt {
// 文件名称
public static String fileName = ".txt";
public static String newFileName = ".txt";
// 文件路径
public final static String URL = System.getProperty("user.dir");
// CreateAndReadTxt.class.getResource("/").getPath();
// 创建TXT文件
public static void createTxtFile(String fName, String fileContent) {
// 创建文件
fileName = fName + fileName;
File file = new File(fileName);
// 可以更改
file.setWritable(true);
// 判断当前路径下是否存在同名文件
boolean isExist = file.exists();
if (isExist) {
// 文件存在,删除
file.delete();
}
// 写入文件
try {
// 文件写入对象
FileOutputStream fos = new FileOutputStream(file);
// 输入流写入----默认字符为GBK
OutputStreamWriter osw = new OutputStreamWriter(fos);
// 写入
osw.write(fileContent);
// 写入完毕后关闭
osw.close();
System.out.println("成功创建文件:\t"+fileName);
} catch (IOException e) {
System.out.println("写入文件失败:\t" + e.getMessage());
}
}
// 阅读文件
public static void readFile(String fileName) {
System.out.println("开始读取文件:\t" + fileName);
// 产生文件对象
File file = new File(fileName);
//
try {
// 字符读取
FileReader fr = new FileReader(file);
// 缓冲处理
BufferedReader br = new BufferedReader(fr);
String str = "";
while ((str = br.readLine()) != null) {
System.out.println(str);
}
// 关闭
br.close();
fr.close();
} catch (FileNotFoundException e) {
System.out.println("读取文件失败:\t" + e.getMessage());
} catch (IOException e) {
System.out.println("读取文件失败:\t" + e.getMessage());
}
}
// 文件复制
public static void copyFile(String fromFileName,String toFileName){
//读取文件
File file = new File(fromFileName);
try {
FileReader fr = new FileReader(file);
BufferedReader br = new BufferedReader(fr);
// 定义接收变量
VectorDouble vec = new VectorDouble();
String s = "";
while(null!=(s=br.readLine())){
vec.add(Double.parseDouble(s));
}
br.close();
fr.close();
// 保存到数组并进行排序
Double dou[] = new Double[vec.size()];
vec.toArray(dou);
Arrays.sort(dou);
System.out.println("========复制文件=========");
// 写入新文件
newFileName = "副本"+newFileName;
File newFile = new File(toFileName);
FileOutputStream fos = new FileOutputStream(newFile, true);
OutputStreamWriter osm = new OutputStreamWriter(fos);
for(Double d:dou){
osm.write(d.doubleValue()+"\n");
}
osm.close();
fos.close();
} catch (FileNotFoundException e) {
System.out.println("读取文件失败:\t" + e.getMessage());
} catch (IOException e) {
System.out.println("读取文件失败:\t" + e.getMessage());
}
}
public static void main(String[] args) {
/**
* 构造数据
*/
Scanner scan = new Scanner(System.in);
StringBuilder sb = new StringBuilder();
String s = "";
while(!("end".equals(s = scan.next()))){// 当输入end时,结束
sb.append(s);
sb.append("\n");
}
scan.close();
/**
* 使用数据
*/
CreateAndReadTxt.createTxtFile("creat", sb.toString());
CreateAndReadTxt.readFile(fileName);
System.out.println(fileName);
CreateAndReadTxt.copyFile(fileName, newFileName);
CreateAndReadTxt.readFile(newFileName);
}
}
Java文件读写
实用的模糊(通配符)文件查找程序
1 import java.io.File;
2 import java.util.regex.Matcher;
3 import java.util.regex.Pattern;
4 import java.util.ArrayList;
5
6 /** *//**
7 * pTitle: FileService /p
8* pDescription: 获取文件 /p
9* pCopyright: Copyright (c) 2007/p
10* pCompany: /p
11* @author not attributable
12* @version 1.0
13*/
14public class FileService {
15 public FileService() {
16 }
17
18 /** *//**
19 * 在本文件夹下查找
20 * @param s String 文件名
21 * @return File[] 找到的文件
22 */
23 public static File[] getFiles(String s)
24 {
25 return getFiles("./",s);
26 }
27
28 /** *//**
29 * 获取文件
30 * 可以根据正则表达式查找
31 * @param dir String 文件夹名称
32 * @param s String 查找文件名,可带*.?进行模糊查询
33 * @return File[] 找到的文件
34 */
35 public static File[] getFiles(String dir,String s) {
36 //开始的文件夹
37 File file = new File(dir);
38
39 s = s.replace('.', '#');
40 s = s.replaceAll("#", "\\\\.");
41 s = s.replace('*', '#');
42 s = s.replaceAll("#", ".*");
43 s = s.replace('?', '#');
44 s = s.replaceAll("#", ".?");
45 s = "^" + s + "$";
46
47 System.out.println(s);
48 Pattern p = Pattern.compile(s);
49 ArrayList list = filePattern(file, p);
50
51 File[] rtn = new File[list.size()];
52 list.toArray(rtn);
53 return rtn;
54 }
55
56 /** *//**
57 * @param file File 起始文件夹
58 * @param p Pattern 匹配类型
59 * @return ArrayList 其文件夹下的文件夹
60 */
61
62 private static ArrayList filePattern(File file, Pattern p) {
63 if (file == null) {
64 return null;
65 }
66 else if (file.isFile()) {
67 Matcher fMatcher = p.matcher(file.getName());
68 if (fMatcher.matches()) {
69 ArrayList list = new ArrayList();
70 list.add(file);
71 return list;
72 }
73 }
74 else if (file.isDirectory()) {
75 File[] files = file.listFiles();
76 if (files != null files.length 0) {
77 ArrayList list = new ArrayList();
78 for (int i = 0; i files.length; i++) {
79 ArrayList rlist = filePattern(files[i], p);
80 if (rlist != null) {
81 list.addAll(rlist);
82 }
83 }
84 return list;
85 }
86 }
87 return null;
88 }
89
90 /** *//**
91 * 测试
92 * @param args String[]
93 */
94 public static void main(String[] args) {
95 }
96}
求用java读写properties文件的代码
Java代码
package com.LY;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.Properties;
public class TestMain {
// 根据key读取value
public static String readValue(String filePath, String key) {
Properties props = new Properties();
try {
InputStream in = new BufferedInputStream(new FileInputStream(
filePath));
props.load(in);
String value = props.getProperty(key);
System.out.println(key + value);
return value;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
// 读取properties的全部信息
public static void readProperties(String filePath) {
Properties props = new Properties();
try {
InputStream in = new BufferedInputStream(new FileInputStream(
filePath));
props.load(in);
Enumeration en = props.propertyNames();
while (en.hasMoreElements()) {
String key = (String) en.nextElement();
String Property = props.getProperty(key);
System.out.println(key + Property);
}
} catch (Exception e) {
e.printStackTrace();
}
}
// 写入properties信息
public static void writeProperties(String filePath, String parameterName,
String parameterValue) {
Properties prop = new Properties();
try {
InputStream fis = new FileInputStream(filePath);
// 从输入流中读取属性列表(键和元素对)
prop.load(fis);
// 调用 Hashtable 的方法 put。使用 getProperty 方法提供并行性。
// 强制要求为属性的键和值使用字符串。返回值是 Hashtable 调用 put 的结果。
OutputStream fos = new FileOutputStream(filePath);
prop.setProperty(parameterName, parameterValue);
// 以适合使用 load 方法加载到 Properties表中的格式,
// 将此 Properties 表中的属性列表(键和元素对)写入输出流
prop.store(fos, "Update '" + parameterName+ "' value");
} catch (IOException e) {
System.err.println("Visit " + filePath + " for updating "
+ parameterName + " value error");
}
}
public static void main(String[] args) {
readValue("info.properties", "url");
writeProperties("info.properties", "age","22");
readProperties("info.properties");
System.out.println("OK");
}
}
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