java.io.File listFiles(FilenameFilter filter)

Description

On this document we will be showing a java example on how to use the listFiles(FilenameFilter filter) method of File Class. This method returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter. The behavior of this method is the same as that of the listFiles() method, except that the pathnames in the returned array must satisfy the filter. If the given filter is null then all pathnames are accepted. Otherwise, a pathname satisfies the filter if and only if the value true results when the FilenameFilter.accept(File, String) method of the filter is invoked on this abstract pathname and the name of a file or directory in the directory that it denotes.

Throws:

SecurityException – If a security manager exists and its SecurityManager.checkRead(String) method denies read access to the directory.

Method Syntax

public File[] listFiles(FilenameFilter filter)

Method Argument

Data Type Parameter Description
FilenameFilter filter A filename filter

Method Returns

This method returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname. The array will be empty if the directory is empty. Returns null if this abstract pathname does not denote a directory, or if an I/O error occurs.

Compatibility

Requires Java 1.2 and up

Java File listFiles(FilenameFilter filter) Example

Below is a java code┬ádemonstrates the use of listFiles(FilenameFilter filter)┬ámethod of File class. The example presented might be simple however it shows the behaviour of the listFiles(FilenameFilter filter)┬ámethod of File class. Because the listFiles(FilenameFilter filter) method returns an array of String the denotes the filenames inside the directory if and only if the abstract pathname denotes directory, thus we have first put a check if the file is a directory or not. It wouldn’t make sense to just blindly list down the filenames without making sure that the pathname is a directory because the returned value would be null. Make sure to have it checked out to avoid unnecessary issues in using this method.The filter that we have used is to list down all files and directories that starts with string “test”.

Sample Output

Below is the sample output when you run the above example.

java lang File listFiles(FilenameFilter filter) example output

Suggested Reading List

References