import java.io.*;
public class FileTest 
{
	public static void main(String[] args) throws IOException
	{
		//以当前路径来创建一个File对象
		File file = new File(".");
		//直接获取文件名,输出一点
		System.out.println(file.getName());
		//获取相对路径的父路径可能出错,下面输出null
		System.out.println(file.getParent());
		//获取绝对路径  
		System.out.println(file.getAbsoluteFile());
		//获取上一级路径
		System.out.println(file.getAbsoluteFile().getParent());
		//在当前路径下创建一个临时文件
		File tmpFile = File.createTempFile("aaa",".txt",file);
		//指定当JVM退出时删除该文件
		tmpFile.deleteOnExit();
		//以系统当前时间为文件名创建一个新文件
		File newFile = new File(System.currentTimeMillis() + "");
		System.out.println("newFile对象是否存在" + newFile.exists());
		//以指定newFile对象来创建一个文件
		newFile.createNewFile();
		//以newFile对象来创建一个目录,因为newFile对象已经存在
		//所以下面方法传回false,无法创建该目录
		newFile.mkdir();
		//用List方法来列出当前路径下所有文件和路径
		String[] fileList = file.list();
		System.out.println("====当前路径下的所有文件和路径如下====");
		for(String fileName : fileList)
		{
			System.out.println(fileName);
		}
		//listRoots方法列出所有的磁盘根路径
		File[] roots = File.listRoots();
                System.out.println("====系统所有根路径如下====");
		for(File root : roots)
		{
			System.out.println(root);
		}
	}
}

输出:

.

null
D:\EditPlus 3\.
D:\EditPlus 3
newFile对象是否存在false
====当前路径下的所有文件和路径如下====
1331536523876
949.chm
aaa8779759108433075606.txt
ansi.ctl
Apple.class
Apple.java
Apple.java.bak
codepage.txt
combobox_u.ini
control.ctl
cpp.acp
cpp.stx
CreateInnerInstance.class
CreateInnerInstance.java
CreateInnerInstance.java.bak
cs.stx
css.stx
css2.ctl
DiscernVariable$1.class
DiscernVariable$InClass.class
DiscernVariable.class
DiscernVariable.java
DiscernVariable.java.bak
editplus.chm
editplus.exe
editplus_u.ini
eppie.exe
eppshell.dll
eppshell64.dll
eppshellreg.exe
FileTest.class
FileTest.java
FileTest.java.bak
Gender$1.class
Gender$2.class
Gender.class
Gender.java
Gender.java.bak
GenderDesc.class
GenderDesc.java
html.stx
html4.ctl
htmlbar.acp
java.acp
java.stx
js.stx
jsp.stx
launcher.exe
Leaf.class
Leaf.java
license-kr.txt
license.txt
LocalInnerClass$1InnerBase.class
LocalInnerClass$1InnerSub.class
LocalInnerClass.class
LocalInnerClass.java
Mid.class
Mid.java
old files
Operation$1.class
Operation$2.class
Operation$3.class
Operation$4.class
Operation.class
Operation.java
Operation.java.bak
out$In.class
out.class
Out.java
out.java.bak
perl.acp
perl.stx
Person.class
Person.java
Person.java.bak
php.stx
PrintObject.class
PrintObject.java
Product.class
Product.java
python.stx
readme.txt
reg_u.ini
remove.exe
Root.class
Root.java
Root.java.bak
ruby.acp
ruby.stx
SETUP3.LOG
Singleton.class
Singleton.java
StringTest.class
StringTest.java
SubClass.class
SubClass.java
template.cpp
template.html
template.java
template.pl
templatex.html
Test.class
Test.java
Test.java.bak
TestAnonymous$1.class
TestAnonymous.class
TestAnonymous.java
TestAnonymous.java.bak
TestCollection.class
TestCollection.java
TestCollection.java.bak
TestGender.class
TestGender.java
TestGender.java.bak
TestScannerKeyBoard.class
TestScannerKeyBoard.java
TestScannerKeyBoard.java.bak
TestSingleton.class
TestSingleton.java
TestSingleton.java.bak
TestSynchronized.class
TestSynchronized.java
TestSynchronized.java.bak
TestToString.class
TestToString.java
TestToString.java.bak
TestWeakHashMap.class
TestWeakHashMap.java
tool_u.ini
vb.stx
xhtml.ctl
xhtmlbar.acp
xml.stx
====系统所有根路径如下====
C:\
D:\
E:\
F:\
G:\
H:\