[NIO.2]The Path Class

새롭게 JAVA7 에서 추가된 java.nio.file package는 file I/O관련 되어 직관이고 많은 기능의 Class들을 제공 한다.

물론 기존 java.io package 역시 계속 제공 된다.(@Deprecated 되지 않음)

일명 NIO.2 로 명명된 새로운 package의 사용법에 대하여 알아보는 첫번째 시간으로 오늘은 Path Class에 대해 알아 보자

1. Creating a Path

Path p1 = Paths.get("/tmp/foo");
Path p2 = Paths.get(args[0]);
Path p3 = Paths.get(URI.create("file:///Users/joe/FileTest.java"));
Path p4 = FileSystems.getDefault().getPath("/users/sally");
Path p5 = Paths.get(System.getProperty("user.home"),"logs", "foo.log");

2. Retrieving Information about a Path

2.1 absolute path

// None of these methods requires that the file corresponding
// to the Path exists.
// Microsoft Windows syntax
Path path = Paths.get("C:\\home\\joe\\foo");

// Solaris syntax
Path path = Paths.get("/home/joe/foo");

System.out.format("toString: %s%n", path.toString());
System.out.format("getFileName: %s%n", path.getFileName());
System.out.format("getName(0): %s%n", path.getName(0));
System.out.format("getNameCount: %d%n", path.getNameCount());
System.out.format("subpath(0,2): %s%n", path.subpath(0,2));
System.out.format("getParent: %s%n", path.getParent());
System.out.format("getRoot: %s%n", path.getRoot());

결과 : 

toString: C:\home\joe\foo

getFileName: foo

getName(0): home

getNameCount: 3

subpath(0,2): home\joe

getParent: C:\home\joe

getRoot: C:\

2.2 relative path

// Solaris syntax
Path path = Paths.get("sally/bar");
or
// Microsoft Windows syntax
Path path = Paths.get("sally\\bar");

결과 : 

toString: sally\bar

getFileName: bar

getName(0): sally

getNameCount: 2

subpath(0,2): sally\bar

getParent: sally

getRoot: null

2. Removing Redundancies From a Path

//다음 PATH는 같은 위치를 가리킨다.
Path path1 = Paths.get("/home/./joe/foo");
Path path2 = Paths.get("/home/sally/../joe/foo");

3. Converting a Path

Path p1 = Paths.get("/home/logfile");
// Result is file:///home/logfile
System.out.format("%s%n", p1.toUri());

//절대 경로 
Path fullPath = p1.toAbsolutePath();

//파일이 존재 하는지 확인 하는 명령어.
try {
    Path fp = path.toRealPath();
} catch (NoSuchFileException x) {
    System.err.format("%s: no such" + " file or directory%n", path);
    // Logic for case when file doesn't exist.
} catch (IOException x) {
    System.err.format("%s%n", x);
    // Logic for other sort of file error.
}

4. Joining Two Paths

resolve method는 기존 Path에 추가한 결과 값을 돌려 준다.

// Solaris
Path p1 = Paths.get("/home/joe/foo");
// Result is /home/joe/foo/bar
System.out.format("%s%n", p1.resolve("bar"));

or

// Microsoft Windows
Path p1 = Paths.get("C:\\home\\joe\\foo");
// Result is C:\home\joe\foo\bar
System.out.format("%s%n", p1.resolve("bar"));

// Result is /home/joe
Paths.get("foo").resolve("/home/joe");

5. Creating a Path Between Two Paths

relativeze 는 두개의 주소를 비교하여 차이를 Path로 돌려준다.

Path p1 = Paths.get("joe");
Path p2 = Paths.get("sally");

// Result is ../sally
Path p1_to_p2 = p1.relativize(p2);
// Result is ../joe
Path p2_to_p1 = p2.relativize(p1);

Path p1 = Paths.get("home");
Path p3 = Paths.get("home/sally/bar");
// Result is sally/bar
Path p1_to_p3 = p1.relativize(p3);
// Result is ../..
Path p3_to_p1 = p3.relativize(p1);

6. Comparing Two Paths

Path path = ...;
Path otherPath = ...;
Path beginning = Paths.get("/home");
Path ending = Paths.get("foo");

if (path.equals(otherPath)) {
    // equality logic here
} else if (path.startsWith(beginning)) {
    // path begins with "/home"
} else if (path.endsWith(ending)) {
    // path ends with "foo"
}

Path path = ...;
for (Path name: path) {
    System.out.println(name);
}

참고 URL : http://docs.oracle.com/javase/tutorial/essential/io/fileio.html