Java path

File:

File file=new File("a/1.txt");

System.out.println(file.getAbsolutePath());

C:\Media2\java2011\a\1.txt

   
File file2=new File("/a/1.txt");

System.out.println(file2.getAbsolutePath());

C:\a\1.txt

File file3=new File("1.txt");
System.out.println(file3.getAbsolutePath());

C:\Media2\java2011\1.txt   
   
File file4=new File("");
System.out.println(file4.getAbsolutePath());

C:\Media2\java2011

 

new File()不会创建Path

  

  //to search "/C:/Media2/java2011/bin"+package(com/webex/go/CasToken.class);
  URL resource = CasToken.class.getResource("CasToken.class"); 

  //to serach C:/Media2/java2011/bin+"/log4j.properties"  
  URL resource2 = CasToken.class.getResource("/log4j.properties"); 
  
  //to search /C:/Media2/java2011/bin+ no need package.
  URL resource3 = CasToken.class.getClassLoader().getResource(
    "log4j.properties");  

  URL resource4 = CasToken.class.getClassLoader().getResource(
  "com/webex/go/CasToken.class");
  
  URL resource5 = CasToken.class.getClassLoader().getResource(
  "/com/webex/go/CasToken.class");

 
/*  /C:/Media2/java2011/bin/com/webex/go/CasToken.class
  /C:/Media2/java2011/bin/log4j.properties
  /C:/Media2/java2011/bin/log4j.properties
  /C:/Media2/java2011/bin/com/webex/go/CasToken.class

  Exception in thread "main" java.lang.NullPointerException
   at com.webex.go.CasToken.main(CasToken.java:40)*/

  

 总结：

File与Classloader用到的PATH一致：

（1）不加任何/，从系统PATH找起，CLASSLOADER是java.class.path=C:\Media2\java2011\bin,  FILE是user.dir=C:\Media2\java2011

  (2)  加/在开头，即/绝对路径

而类字面常量String.class..getResourceAsStream,比较特殊：用到的PATH:

（1）不加任何/，从系统PATH（C:/Media2/java2011/bin）+当前包下找起， 

  (2)  加/在开头，从系统PATH（C:/Media2/java2011/bin）下找起。 

InputStream java.lang.Class.getResourceAsStream(String name)

If the name begins with a '/' ('\u002f'), then the absolute name of the resource is the portion of the name following the '/'.
Otherwise, the absolute name is of the following form:
   modified_package_name/name
 
Where the modified_package_name is the package name of this object with '/' substituted for '.' ('\u002e'). 

URL java.lang.Class.getResource(String name)

普通classLoder/path

/绝对，   无/相对  bin或者项目名称

getResponse

              /  bin下面    无/包下面