What’s the Time Stamp of a File?

JDK 1.1.x’s java.io.File class has a lastModified():long method. You can use the value returned by lastModified method to create an instance of java.util.Date class and, thus, get a hold of date/time of last modifications for a file.Here is some sample code that prints the last modification of files in current user directory:

 public void printCurDirContent() { String path = "."; File f = new File(path); String[] s = f.list(); for(int i=0; i

JDK's documentation mentions that the return value of lastModified() method of the File class is "system-dependent and should only be used to compare with other values returned by last modified". So if you use to compare time/date stamps of files, make sure that you execute the method on your files on the same system.

As of JDK 1.2, a new method, setLastModified(:long):boolean, has been added to java.util.File class. You can use this method to change the last modification time of a file. Here is some code showing how:

 public static void touch(String filePath) { long timeNow = System.currentTimeMillis(); File f = new File(filePath); boolean touched = f.setLastModified(timeNow); if (!touched) { System.err.println("Failed to touch: "+ filePath); } } 

Note that the return value of lastModified method and the parameter value of setLastModified(...) method are times measured in milliseconds since January 1, 1970 00:00:00 GMT.

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