求一个有关文件的程序 一直都被文件困扰着。希望大家能给个文件的程序。要求能向文件中添加数据和读出数据。用inputstream和outputstream。写入文件时判断文件是否存在。若存在则直接在文件末尾添加数据,否则创建一个文件。希望文件方面需要注意的知识越全面越好。谢谢 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 LZ你好有爱InputStream is = new FileInputStream("文件路径",true);就会自动识别了,没有就创建,有就在末尾添加....外面再加上各种各样的处理流吧,多看看JDK 纠正:打错了 囧OutputStream is = new FileOutputStream("文件路径",true); import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;public class FileUtil { /*** * 将指定文件中的信息读取到一个字节数组中 * @param fileName * @return * @throws IOException */ public byte[]loadFileData(String fileName)throws IOException{ byte[] filedate = new byte[1000]; File fileIn = new File(fileName); if(fileIn.exists()){ FileInputStream input = new FileInputStream(fileIn); input.read(filedate); input.close(); } else{ System.out.println("文件不存在"); } return filedate; } /*** * 将字节数组的信息保存到相应的文件中,同时记录所读取的字节数 * @param fileName * @param data * @throws IOException */ public void saveDataToFile(String fileName,byte[]data)throws IOException{ int byteNum; File fileOut = new File(fileName); if(!fileOut.exists()){ fileOut.createNewFile(); } FileOutputStream out = new FileOutputStream(fileOut); out.write(data); out.close(); } } 读写很简单,乱写的:package test;import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.File;import java.io.FileInputStream;import java.io.FileWriter;import java.io.IOException;import java.io.InputStreamReader;public class ReadWriteListFile { public static void main(String[] args) throws Exception { try { String fileName = "E:\\result.dat"; String contents = "ReadWriteListFile.formatLst(lst)"; saveFile(fileName, contents); String a = readFile(fileName); System.out.println(a); } catch (Exception e) { e.printStackTrace(); } } public static String readFile(String fileName) throws Exception { String contents = ""; String s = ""; File f = new File(fileName); if (!f.exists()) { throw new Exception("file doesn't exist...."); } BufferedReader br = null; try { br = new BufferedReader(new InputStreamReader( new FileInputStream(f))); while ((s = br.readLine()) != null) { contents += s + "\n"; } System.out.println("read file finished"); } catch (Exception e) { throw e; } finally { try { br.close(); } catch (Exception e) { } } return contents; } static void saveFile(String fileName, String contents) throws IOException { File f = new File(fileName); BufferedWriter output = null; try { // 如果不存在 if (!f.exists()) { // 建新文件 if (!f.createNewFile()) { throw new IOException("file create failure..."); } } // 这里的 true表示文件追加,false表示原来的都不要 output = new BufferedWriter(new FileWriter(f, true)); output.write(contents); } catch (Exception e) { e.printStackTrace(); } finally { // 最后在finally关闭 try { output.close(); } catch (Exception e) { } } }} 求一个快速排列出所有字符串组合的方法 readLine的问题 运行两个应用程序如何实现数据同步 对JAVA的困惑?? 初学java 一个很小的问题关于servlet drill down at INT type. 读取一个1000万行的文件 新手上路-怎么用JDK?-20分 To masterz():本人愚笨,向你再请教一个问题 在静态上下文中不能引用非静态变量 this java 把坐标值对转换成double数组 Java SocketChannel.write
InputStream is = new FileInputStream("文件路径",true);
就会自动识别了,没有就创建,有就在末尾添加....外面再加上各种各样的处理流吧,多看看JDK
OutputStream is = new FileOutputStream("文件路径",true);
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;public class FileUtil {
/***
* 将指定文件中的信息读取到一个字节数组中
* @param fileName
* @return
* @throws IOException
*/
public byte[]loadFileData(String fileName)throws IOException{
byte[] filedate = new byte[1000];
File fileIn = new File(fileName);
if(fileIn.exists()){
FileInputStream input = new FileInputStream(fileIn);
input.read(filedate);
input.close();
}
else{
System.out.println("文件不存在");
}
return filedate;
}
/***
* 将字节数组的信息保存到相应的文件中,同时记录所读取的字节数
* @param fileName
* @param data
* @throws IOException
*/
public void saveDataToFile(String fileName,byte[]data)throws IOException{
int byteNum;
File fileOut = new File(fileName);
if(!fileOut.exists()){
fileOut.createNewFile();
}
FileOutputStream out = new FileOutputStream(fileOut);
out.write(data);
out.close();
}
}
package test;import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;public class ReadWriteListFile {
public static void main(String[] args) throws Exception { try { String fileName = "E:\\result.dat";
String contents = "ReadWriteListFile.formatLst(lst)";
saveFile(fileName, contents);
String a = readFile(fileName);
System.out.println(a);
} catch (Exception e) {
e.printStackTrace();
}
} public static String readFile(String fileName) throws Exception {
String contents = "";
String s = "";
File f = new File(fileName);
if (!f.exists()) {
throw new Exception("file doesn't exist....");
}
BufferedReader br = null;
try {
br = new BufferedReader(new InputStreamReader(
new FileInputStream(f))); while ((s = br.readLine()) != null) {
contents += s + "\n";
} System.out.println("read file finished");
} catch (Exception e) {
throw e;
} finally {
try {
br.close();
} catch (Exception e) { }
}
return contents;
} static void saveFile(String fileName, String contents) throws IOException {
File f = new File(fileName);
BufferedWriter output = null;
try {
// 如果不存在
if (!f.exists()) {
// 建新文件
if (!f.createNewFile()) {
throw new IOException("file create failure...");
}
}
// 这里的 true表示文件追加,false表示原来的都不要
output = new BufferedWriter(new FileWriter(f, true));
output.write(contents); } catch (Exception e) {
e.printStackTrace();
} finally {
// 最后在finally关闭
try {
output.close(); } catch (Exception e) { }
}
}
}