Apache Commons IO framework file filtering and finding technical principles analysis
Apache Commons IO is an open source framework for Java programmers with common I/O operations.It contains some file filtering and search functions. In this article, we will deeply analyze the technical principles of filtering and searching in the Apache Commons IO framework in Chinese.
In the Apache Commons IO framework, file filtering and search are mainly achieved by using the two classes of FileFilter and Fileutils.The FileFilter interface defines a method.The FileUtils class provides a series of static methods to find files that meet the filtration conditions.
The process of file filtering and search can be divided into the following steps:
1. Create a file object, indicating the root directory of filtering and searching.
File rootDir = new File("path/to/root/directory");
2. Create a class that implements the FileFilter interface to define the filtering conditions.You can use some static methods provided by the FileFilterutils class to create common filtering conditions, such as filtering by file extension, filtering by file name prefix.
FileFilter filter = FileFilterUtils.and(
FileFilterutils.filefilefilter (), // only find files, excluding directory
Filefilterutils.suffixFileFilter (". Txt") // File extension name .txt
);
3. Call the static method of FileUtils to find the file.You can use the FileUtils.ListFiles method to find all files that meet the filtering conditions, or you can use the FileUtils. ListFilesandDIRS method to find files and directory that meets the filtering conditions.
Collection<File> files = FileUtils.listFiles(rootDir, filter, null);
for (File file : files) {
// Treatment the files that meet the filtration conditions
}
Through the above steps, we can easily implement the file filtering and search function.Below is a complete sample code, which is used to find a text file with all extension named .txt in a directory:
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.filefilter.FileFilterUtils;
import org.apache.commons.io.filefilter.IOFileFilter;
import java.io.File;
import java.util.Collection;
public class FileSearchExample {
public static void main(String[] args) {
File rootDir = new File("path/to/root/directory");
IOFileFilter filter = FileFilterUtils.and(
FileFilterUtils.fileFileFilter(),
FileFilterUtils.suffixFileFilter(".txt")
);
Collection<File> files = FileUtils.listFiles(rootDir, filter, null);
for (File file : files) {
System.out.println(file.getAbsolutePath());
}
}
}
To sum up, the Apache Commons IO framework provides file filtering and finding functions through Filefilter and FileUtils.We can create customized filtering conditions according to actual needs, and then use FileUtils to find operations.The use of this framework makes the implementation of file filtering and finding more simple and efficient.
