java中获取路径的几种方式

总是忘记， 备份一下，方便下次用.

第一种：

File directory = new File("");//参数为空

String courseFile = directory.getCanonicalPath() ;System.out.println(courseFile);

结果：C:\Documents and Settings\Administrator\workspace\projectName获取当前类的所在工程路径;

第二种：

File f = new File(this.getClass().getResource("/").getPath());

System.out.println(f);

结果:C:\Documents and Settings\Administrator\workspace\projectName\bin

如果不加“/”

File f = new File(this.getClass().getResource("").getPath());

System.out.println(f);

结果：C:\Documents and Settings\Administrator\workspace\projectName\bin\com\test

第三种：URL xmlpath = this.getClass().getClassLoader().getResource("selected.txt");

System.out.println(xmlpath);

结果：file:/C:/Documents and Settings/Administrator/workspace/projectName/bin/selected.txt

第四种：

System.out.println(System.getProperty("user.dir"));

结果：C:\Documents and Settings\Administrator\workspace\projectName

第五种：System.out.println( System.getProperty("java.class.path"));

结果：C:\Documents and Settings\Administrator\workspace\projectName\bin

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.RandomAccessFile;  

public class FileOperation {  

 /**
  * 创建文件
  * @param fileName
  * @return
  */
 public static boolean createFile(File fileName)throws Exception{
  boolean flag=false;
  try{
   if(!fileName.exists()){
    fileName.createNewFile();
    flag=true;
   }
  }catch(Exception e){
   e.printStackTrace();
  }
  return true;
 }   

 /**
  * 读TXT文件内容
  * @param fileName
  * @return
  */
 public static String readTxtFile(File fileName)throws Exception{
  String result=null;
  FileReader fileReader=null;
  BufferedReader bufferedReader=null;
  try{
   fileReader=new FileReader(fileName);
   bufferedReader=new BufferedReader(fileReader);
   try{
    String read=null;
    while((read=bufferedReader.readLine())!=null){
     result=result+read+"\r\n";
    }
   }catch(Exception e){
    e.printStackTrace();
   }
  }catch(Exception e){
   e.printStackTrace();
  }finally{
   if(bufferedReader!=null){
    bufferedReader.close();
   }
   if(fileReader!=null){
    fileReader.close();
   }
  }
  System.out.println("读取出来的文件内容是："+"\r\n"+result);
  return result;
 }  

 public static boolean writeTxtFile(String content,File  fileName)throws Exception{
  RandomAccessFile mm=null;
  boolean flag=false;
  FileOutputStream o=null;
  try {
   o = new FileOutputStream(fileName);
      o.write(content.getBytes("GBK"));
      o.close();
//   mm=new RandomAccessFile(fileName,"rw");
//   mm.writeBytes(content);
   flag=true;
  } catch (Exception e) {
   // TODO: handle exception
   e.printStackTrace();
  }finally{
   if(mm!=null){
    mm.close();
   }
  }
  return flag;
 }  

public static void contentToTxt(String filePath, String content) {
        String str = new String(); //原有txt内容
        String s1 = new String();//内容更新
        try {
            File f = new File(filePath);
            if (f.exists()) {
                System.out.print("文件存在");
            } else {
                System.out.print("文件不存在");
                f.createNewFile();// 不存在则创建
            }
            BufferedReader input = new BufferedReader(new FileReader(f));  

            while ((str = input.readLine()) != null) {
                s1 += str + "\n";
            }
            System.out.println(s1);
            input.close();
            s1 += content;  

            BufferedWriter output = new BufferedWriter(new FileWriter(f));
            output.write(s1);
            output.close();
        } catch (Exception e) {
            e.printStackTrace();  

        }
    }  

}