DiskCache2 (All javadoc for netcdf-java version 4.6.22-SNAPSHOT)

java.lang.Object
- ucar.nc2.util.DiskCache2

```
public class DiskCache2
extends java.lang.Object
```
Manages a place on disk to persistently cache files, which are deleted when the last modified date exceeds a certain time. This starts up a thread to periodically scour itself; be sure to call exit() to terminate the thread.
Each DiskCache has a "root directory", which may be set as an absolute path, or reletive to the DiskCache "home directory". The root directory must be writeable. The DiskCache home directory is set in the following order:
1. through the system property "nj22.cache" if it exists
2. through the system property "user.home" if it exists
3. through the system property "user.dir" if it exists
4. to the current working directory

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class DiskCache2.CachePathPolicy

Nested Classes
Modifier and Type	Class and Description
`static class`	`DiskCache2.CachePathPolicy`

Constructor Summary

Constructors
Constructor and Description
`DiskCache2(java.lang.String root, boolean reletiveToHome, int persistMinutes, int scourEveryMinutes)` Create a cache on disk.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`static boolean`	`canWrite(java.io.File f)` Returns `true` if we can write to the file.
`void`	`cleanCache(java.io.File dir, java.lang.StringBuilder sbuff, boolean isRoot)` Remove any files or directories whose last modified time greater than persistMinutes
`java.io.File`	`createUniqueFile(java.lang.String prefix, java.lang.String suffix)` Reserve a new, uniquely named file in the root directory.
`void`	`exit()` Be sure to call this when your application exits, otherwise the scour thread may not die.
`java.io.File`	`getCacheFile(java.lang.String fileLocation)` Get a File in the cache, corresponding to the fileLocation.
`static DiskCache2`	`getDefault()` Default DiskCache2 strategy: use $user_home/.unidata/cache/, no scouring, alwaysUseCache = false Mimics default DiskCache static class
`java.io.File`	`getExistingFileOrCache(java.lang.String fileLocation)` Looking for an existing file, in cache or no
`java.io.File`	`getFile(java.lang.String fileLocation)` Get the named File.
`static DiskCache2`	`getNoop()`
`java.lang.String`	`getRootDirectory()` Get the cache root directory.
`void`	`setAlwaysUseCache(boolean alwaysUseCache)` If true, always put the file in the cache.
`void`	`setCachePathPolicy(DiskCache2.CachePathPolicy cachePathPolicy, java.lang.String cachePathPolicyParam)` Set the cache path policy
`void`	`setCachePathPolicy(int cachePathPolicy, java.lang.String cachePathPolicyParam)` Deprecated. use setCachePathPolicy(CachePathPolicy cachePathPolicy, String cachePathPolicyParam)
`void`	`setLogger(org.slf4j.Logger cacheLog)` Optionally set a logger.
`void`	`setNeverUseCache(boolean neverUseCache)` If true, never put the file in the cache.
`void`	`setPolicy(DiskCache2.CachePathPolicy cachePathPolicy)` Set the cache path policy
`void`	`setPolicy(int cachePathPolicy)` Deprecated. use setCachePathPolicy(CachePathPolicy cachePathPolicy)
`void`	`setPolicy(java.lang.String policy)`
`void`	`setRootDirectory(java.lang.String cacheDir)`
`void`	`showCache(java.io.PrintStream pw)` Show cache contents.
`java.lang.String`	`toString()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - DiskCache2
```
public DiskCache2(java.lang.String root,
                  boolean reletiveToHome,
                  int persistMinutes,
                  int scourEveryMinutes)
```
    Create a cache on disk. Use default policy (CachePathPolicy.NestedDirectory)
    
    Parameters:
    
    root - the root directory of the cache. Must be writeable.
    
    reletiveToHome - if the root directory is relative to the cache home directory.
    
    persistMinutes - a file is deleted if its last modified time is greater than persistMinutes
    
    scourEveryMinutes - how often to run the scour process. If <= 0, don't scour.
- Method Detail
  - getDefault
```
public static DiskCache2 getDefault()
```
    Default DiskCache2 strategy: use $user_home/.unidata/cache/, no scouring, alwaysUseCache = false Mimics default DiskCache static class
  - getNoop
```
public static DiskCache2 getNoop()
```
  - exit
```
public void exit()
```
    Be sure to call this when your application exits, otherwise the scour thread may not die.
  - setLogger
```
public void setLogger(org.slf4j.Logger cacheLog)
```
    Optionally set a logger. Each time a scour is done, a messsage is written to it.
    
    Parameters:
    
    cacheLog - use this logger
  - setRootDirectory
```
public void setRootDirectory(java.lang.String cacheDir)
```
  - getRootDirectory
```
public java.lang.String getRootDirectory()
```
    Get the cache root directory.
    
    Returns:
    
    the cache root directory.
  - getCacheFile
```
public java.io.File getCacheFile(java.lang.String fileLocation)
```
    Get a File in the cache, corresponding to the fileLocation. File may or may not exist. If fileLocation has "/" in it, and cachePathPolicy == NestedDirectory, the nested directories will be created.
    
    Parameters:
    
    fileLocation - logical file location
    
    Returns:
    
    physical File in the cache.
  - getFile
```
public java.io.File getFile(java.lang.String fileLocation)
```
    Get the named File. If exists or isWritable, return it. Otherwise get corresponding file in the cache directory. If fileLocation has "/" in it, and cachePathPolicy == NestedDirectory, the nested directories will be created.
    
    Parameters:
    
    fileLocation - logical file location
    
    Returns:
    
    physical File as named, or in the cache.
  - canWrite
```
public static boolean canWrite(java.io.File f)
```
    Returns true if we can write to the file.
    
    Parameters:
    
    f - a file. It may be a regular file or a directory. It may even be non-existent, in which case the writability of the file's parent dir is tested.
    
    Returns:
    
    true if we can write to the file.
  - getExistingFileOrCache
```
public java.io.File getExistingFileOrCache(java.lang.String fileLocation)
```
    Looking for an existing file, in cache or no
    
    Parameters:
    
    fileLocation - the original name
    
    Returns:
    
    existing file if you can find it
  - createUniqueFile
```
public java.io.File createUniqueFile(java.lang.String prefix,
                                     java.lang.String suffix)
```
    Reserve a new, uniquely named file in the root directory. Mimics File.createTempFile(), but does not actually create the file. Instead, a 0 byte file of the same name with the extension lock is created, thus "reserving" the name until it is used. The filename must be used before persistMinutes, or the lock will be scoured and the reservation will be lost.
    
    Parameters:
    
    prefix - The prefix string to be used in generating the file's name; must be at least three characters long
    
    suffix - The suffix string to be used in generating the file's name; may be null, in which case the suffix ".tmp" will be used
    
    Returns:
    
    uniquely named file
  - setPolicy
```
public void setPolicy(DiskCache2.CachePathPolicy cachePathPolicy)
```
    Set the cache path policy
    
    Parameters:
    
    cachePathPolicy - one of: OneDirectory (default) : replace "/" with "-", so all files are in one directory. NestedDirectory: cache files are in nested directories under the root. NestedTruncate: eliminate leading directories
  - setCachePathPolicy
```
public void setCachePathPolicy(DiskCache2.CachePathPolicy cachePathPolicy,
                               java.lang.String cachePathPolicyParam)
```
    Set the cache path policy
    
    Parameters:
    
    cachePathPolicy - one of: OneDirectory (default) : replace "/" with "-", so all files are in one directory. NestedDirectory: cache files are in nested directories under the root. NestedTruncate: eliminate leading directories
    
    cachePathPolicyParam - for NestedTruncate, eliminate this string
  - setCachePathPolicy
```
public void setCachePathPolicy(int cachePathPolicy,
                               java.lang.String cachePathPolicyParam)
```
    Deprecated. use setCachePathPolicy(CachePathPolicy cachePathPolicy, String cachePathPolicyParam)
  - setPolicy
```
public void setPolicy(int cachePathPolicy)
```
    Deprecated. use setCachePathPolicy(CachePathPolicy cachePathPolicy)
  - setPolicy
```
public void setPolicy(java.lang.String policy)
```
  - setAlwaysUseCache
```
public void setAlwaysUseCache(boolean alwaysUseCache)
```
    If true, always put the file in the cache. default false.
    
    Parameters:
    
    alwaysUseCache - If true, always put the file in the cache
  - setNeverUseCache
```
public void setNeverUseCache(boolean neverUseCache)
```
    If true, never put the file in the cache. default false.
    
    Parameters:
    
    neverUseCache - If true, never put the file in the cache
  - showCache
```
public void showCache(java.io.PrintStream pw)
```
    Show cache contents.
    
    Parameters:
    
    pw - write to this PrintStream.
  - cleanCache
```
public void cleanCache(java.io.File dir,
                       java.lang.StringBuilder sbuff,
                       boolean isRoot)
```
    Remove any files or directories whose last modified time greater than persistMinutes
    
    Parameters:
    
    dir - clean starting here
    
    sbuff - status messages here, may be null
    
    isRoot - delete empty directories, bit not root directory
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object

Class DiskCache2

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

DiskCache2

Method Detail

getDefault

getNoop

exit

setLogger

setRootDirectory

getRootDirectory

getCacheFile

getFile

canWrite

getExistingFileOrCache

createUniqueFile

setPolicy

setCachePathPolicy

setCachePathPolicy

setPolicy

setPolicy

setAlwaysUseCache

setNeverUseCache

showCache

cleanCache

toString