java中获取当前路径

import java.io.File;
import java.net.URL;

public class GetCurrentDir {

public String getDirByFile(String var){
try{
System.out.println("[GetCurrentDir][getDirByFile] start>>>");

File file = new File(var);

System.out.println("File file = new File("+var+")");

String dir_getCanonicalPath = file.getCanonicalPath();
String dir_getAbsolutePath = file.getAbsolutePath();
String dir_getPath = file.getPath();

System.out.println("dir_getCanonicalPath: "+dir_getCanonicalPath);
System.out.println("dir_getAbsolutePath: "+dir_getAbsolutePath);
System.out.println("dir_getPath: "+dir_getPath);

System.out.println("[GetCurrentDir][getDirByFile] end<<<");
return dir_getCanonicalPath;
}catch(Exception e){
System.out.println(e.getMessage()+"");
return "";
}
}

public String getDirByClassURL()throws Exception{
System.out.println("[GetCurrentDir][getDirByClassURL] start>>>");

String dir = "";
Class currentClass = this.getClass();
URL url = currentClass.getResource("");
dir = url.toString();

System.out.println("URL url = currentClass.getResource(\"\")"+"\n"+dir);

System.out.println("[GetCurrentDir][getDirByClassURL] end<<<");
return dir;
}

public String getDirBySystem() throws Exception{
System.out.println("[GetCurrentDir][getDirBySystem] start>>>");
String dir = "";
dir = System.getProperty("user.dir");//for more var, please go to end
System.out.println("System.getProperty(\"user.dir\")");
System.out.println("dir: "+dir);
System.out.println("[GetCurrentDir][getDirBySystem] end<<<");
return dir;
}

public static void main(String[] args) {
GetCurrentDir dir = new GetCurrentDir();
try{
dir.getDirByFile(".");
dir.getDirByFile("..");
dir.getDirByFile("");
dir.getDirByFile("D:\\");

System.out.println("\n");
dir.getDirByClassURL();

System.out.println("\n");
dir.getDirBySystem();
}catch(Exception e){
System.out.println(""+e.getMessage());
e.printStackTrace();
}
}

}

//java.version                                Java Runtime Environment version  
//java.vendor                                Java Runtime Environment vendor  
//java.vendor.url                           Java vendor URL  
//java.home                                Java installation directory  
//java.vm.specification.version   Java Virtual Machine specification version  
//java.vm.specification.vendor    Java Virtual Machine specification vendor  
//java.vm.specification.name      Java Virtual Machine specification name  
//java.vm.version                        Java Virtual Machine implementation version  
//java.vm.vendor                        Java Virtual Machine implementation vendor  
//java.vm.name                        Java Virtual Machine implementation name  
//java.specification.version        Java Runtime Environment specification version  
//java.specification.vendor         Java Runtime Environment specification vendor  
//java.specification.name           Java Runtime Environment specification name  
//java.class.version                    Java class format version number  
//java.class.path                      Java class path  
//java.library.path                 List of paths to search when loading libraries  
//java.io.tmpdir                       Default temp file path  
//java.compiler                       Name of JIT compiler to use  
//java.ext.dirs                       Path of extension directory or directories  
//os.name                              Operating system name  
//os.arch                                  Operating system architecture  
//os.version                       Operating system version  
//file.separator                         File separator ("/" on UNIX)  
//path.separator                  Path separator (":" on UNIX)  
//line.separator                       Line separator ("\n" on UNIX)  
//user.name                        User's account name  
//user.home                              User's home directory  
//user.dir                               User's current working directory 
结果：

[GetCurrentDir][getDirByFile] start>>>
File file = new File(.)
dir_getCanonicalPath: D:\work\workspaceForEMS\StudyPrj
dir_getAbsolutePath: D:\work\workspaceForEMS\StudyPrj\.
dir_getPath: .
[GetCurrentDir][getDirByFile] end<<<
[GetCurrentDir][getDirByFile] start>>>
File file = new File(..)
dir_getCanonicalPath: D:\work\workspaceForEMS
dir_getAbsolutePath: D:\work\workspaceForEMS\StudyPrj\..
dir_getPath: ..
[GetCurrentDir][getDirByFile] end<<<
[GetCurrentDir][getDirByFile] start>>>
File file = new File()
dir_getCanonicalPath: D:\work\workspaceForEMS\StudyPrj
dir_getAbsolutePath: D:\work\workspaceForEMS\StudyPrj
dir_getPath:
[GetCurrentDir][getDirByFile] end<<<
[GetCurrentDir][getDirByFile] start>>>
File file = new File(D:\)
dir_getCanonicalPath: D:\
dir_getAbsolutePath: D:\
dir_getPath: D:\
[GetCurrentDir][getDirByFile] end<<<


[GetCurrentDir][getDirByClassURL] start>>>
URL url = currentClass.getResource("")
file:/D:/work/workspaceForEMS/StudyPrj/bin/xml/dom4j/
[GetCurrentDir][getDirByClassURL] end<<<


[GetCurrentDir][getDirBySystem] start>>>
System.getProperty("user.dir")
dir: D:\work\workspaceForEMS\StudyPrj
[GetCurrentDir][getDirBySystem] end<<<