JAVA에서 Unique한 키값 얻어 오기

자바에서 Unique한 키값을 얻어오기 위해서는 UUID라는 기능을 사용하면 된다.
100% Unique한 값을 보장할수는 없지만 거의 유일한 키값을 준다고 한다.

  package com.gsshop.im4java; import java.io.File; import java.util.UUID;  public class UniqueFileName { 	public static void main(String[] args) {         System.out.println(doMakeUniqueFileName("c:\\sample\\","girl.jpg")); 	}  	public static String doMakeUniqueFileName(String serverPath, String fileName) {  		String extension = fileName.substring(fileName.lastIndexOf("."));  		 String uniqueFileName = null;  		 boolean flag = true;  		 while (flag) {  		  uniqueFileName = getUniqueFileName();  		  flag = doCheckFileExists(serverPath+uniqueFileName+extension);  		 }  		 return serverPath+uniqueFileName+extension;  		}  		private static boolean doCheckFileExists(String fullPath) {  		     return new File(fullPath).exists();  		}  		private static String getUniqueFileName() {  		return  UUID.randomUUID().toString();  		}  } 

 

 

UUID API 원문

http://docs.oracle.com/javase/6/docs/api/java/util/UUID.html

public final class UUID

extends Object

implements Serializable, Comparable<UUID>

A class that represents an immutable universally unique identifier (UUID). A UUID represents a 128-bit value.

There exist different variants of these global identifiers. The methods of this class are for manipulating the Leach-Salz variant, although the constructors allow the creation of any variant of UUID (described below).

The layout of a variant 2 (Leach-Salz) UUID is as follows: The most significant long consists of the following unsigned fields:

 0xFFFFFFFF00000000 time_low  0x00000000FFFF0000 time_mid  0x000000000000F000 version  0x0000000000000FFF time_hi  

The least significant long consists of the following unsigned fields:

 0xC000000000000000 variant  0x3FFF000000000000 clock_seq  0x0000FFFFFFFFFFFF node  

The variant field contains a value which identifies the layout of the 

UUID

. The bit layout described above is valid only for a 

UUID

 with a variant value of 2, which indicates the Leach-Salz variant.

The version field holds a value that describes the type of this 

UUID

. There are four different basic types of UUIDs: time-based, DCE security, name-based, and randomly generated UUIDs. These types have a version value of 1, 2, 3 and 4, respectively.

For more information including algorithms used to create 

UUID

s, see RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace, section 4.2 "Algorithms for Creating a Time-Based UUID".

 

 

Since:

1.5

See Also:

Serialized Form