org.apache.commons.io.FileUtils例子

用apache.commons.io 中的一些方法来操作文件，会减轻程序员的很多负担，文件操作经常会用到FileUtils这个类，今天在这里对最常用的一些方法做一个总结，当然最全面的东西，还是应该看apache.commons.io 的文档或者示例。

contentEquals(File file1, File file2): 比较两个文件的内容，返回他们的内容是否相同.
copyDirectory(File source, File destination):从一个文件夹拷贝内容到另外一个文件夹，包括子目录。
copyDirectory(File source, File destination, FileFilter filter): 基本用途类似，但多了一个过滤条件，只拷贝满足条件的文件或子文件夹，比如根据名称，修改时间等过滤
copyFile(File srcFile, File destFile): 拷贝文件
deleteDirectory(File directory): 递归删除文件夹.
getTempDirectory(): 返回系统临时目录.
getUserDirectory(): 返回用户目录.
lineIterator(File file): 返回给定文件，所有的行，可以对所有的行进行循环操作
sizeOfDirectory(File directory): 返回文件夹大小.
writeLines(File file, Collection lines): 写文件，将一个集合里的内容都写到文件中去.

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.LineIterator;
import org.apache.commons.io.filefilter.SuffixFileFilter;

public class FileUtilsExample {
    
    private static final String MAIN_PATH = "C:\\Users\\Lilykos\\Desktop\\FUExFiles\\";

    public static void main(String[] args) throws IOException {
        
        // file1: "Hello World!"
        // file2: "Hello World!!!"
        File file1 = FileUtils.getFile(MAIN_PATH + "cmpFile1.txt");
        File file2 = FileUtils.getFile(MAIN_PATH + "cmpFile2.txt");
        System.out.println("Are cmpFile1 and cmpFile2 equal: " +
                FileUtils.contentEquals(file1, file2));
        
        
        // We can copy a whole path somewhere
        // and check if the operation was successful.
        FileUtils.copyDirectory(
                FileUtils.getFile(MAIN_PATH),                   // source
                FileUtils.getFile(MAIN_PATH + "copiedPath\\")); // destination
        
        System.out.println("Does the copiedPath exist: " +
                FileUtils.getFile(MAIN_PATH + "copiedPath\\").exists());
        
        
        // Copy a directory by filtering out all the txt files.
        // In the directory right now: cmpFile1.txt, cmpFile2.txt, zipFile.zip
        FileUtils.copyDirectory(
                FileUtils.getFile(MAIN_PATH),
                FileUtils.getFile(MAIN_PATH + "copiedFilterPath\\"),
                new SuffixFileFilter(".zip"));
        
        for (File f: FileUtils.getFile(MAIN_PATH + "copiedFilterPath\\").listFiles()) {
            System.out.println("Contents of copiedFilterPath: " + f.getName());
        }
        
        
        // Copy a file
        File copy = FileUtils.getFile(MAIN_PATH + "copyOfFile1.txt");
        FileUtils.copyFile(file1, copy);
        System.out.println("Are cmpFile1 and copyOfFile1 equal: " +
                FileUtils.contentEquals(file1, copy));
        
        
        // Right now there are these files in the MAIN_PATH.
        for (File f: FileUtils.getFile(MAIN_PATH).listFiles()) {
            System.out.println("Contents of MAIN_PATH: " + f.getName());
        }
        // Let's delete a directory and see the results.
        FileUtils.deleteDirectory(FileUtils.getFile(MAIN_PATH + "copiedFilterPath\\"));
        for (File f: FileUtils.getFile(MAIN_PATH).listFiles()) {
            System.out.println("Contents of MAIN_PATH after deletion: " + f.getName());
        }
        
        
        // Directories
        System.out.println("Temp Dir: " +
                FileUtils.getTempDirectory().getAbsolutePath());
        System.out.println("User Dir: " +
                FileUtils.getUserDirectory().getAbsolutePath());
        
        
        // Line Iterator
        LineIterator iter = FileUtils.lineIterator(file1);
        while (iter.hasNext()) {
            System.out.println("cmpFile1 lines: " + iter.next());
        }
        
        
        // Directory size
        System.out.println("Size of dir: " +
                FileUtils.sizeOfDirectory(FileUtils.getFile(MAIN_PATH)) +
                " bytes.");
        
        
        // Ways of writing lines to a file.
        File fileToWrite1 = FileUtils.getFile(MAIN_PATH + "fileToWrite1.txt");
        File fileToWrite2 = FileUtils.getFile(MAIN_PATH + "fileToWrite2.txt");
        
        Collection lines = new ArrayList<>();
        lines.add("Written with FileUtils!");
        lines.add("For Java Code Geeks.");
        
        FileUtils.write(fileToWrite1, "Written with FileUtils!");
        FileUtils.writeLines(fileToWrite2, lines);
        
        iter = FileUtils.lineIterator(fileToWrite1);
        while (iter.hasNext()) {
            System.out.println("fileToWrite1 lines: " + iter.next());
        }
        iter = FileUtils.lineIterator(fileToWrite2);
        while (iter.hasNext()) {
            System.out.println("fileToWrite2 lines: " + iter.next());
        }
    }
}

Are cmpFile1 and cmpFile2 equal: false
Does the copiedPath exist: true
Contents of copiedFilterPath: zipFile.zip
Are cmpFile1 and copyOfFile1 equal: true
Contents of MAIN_PATH: cmpFile1.txt
Contents of MAIN_PATH: cmpFile2.txt
Contents of MAIN_PATH: copiedFilterPath
Contents of MAIN_PATH: copiedPath
Contents of MAIN_PATH: copyOfFile1.txt
Contents of MAIN_PATH: fileToWrite1.txt
Contents of MAIN_PATH: fileToWrite2.txt
Contents of MAIN_PATH: zipFile.zip
Contents of MAIN_PATH after deletion: cmpFile1.txt
Contents of MAIN_PATH after deletion: cmpFile2.txt
Contents of MAIN_PATH after deletion: copiedPath
Contents of MAIN_PATH after deletion: copyOfFile1.txt
Contents of MAIN_PATH after deletion: fileToWrite1.txt
Contents of MAIN_PATH after deletion: fileToWrite2.txt
Contents of MAIN_PATH after deletion: zipFile.zip
Temp Dir: C:\Users\Lilykos\AppData\Local\Temp
User Dir: C:\Users\Lilykos
cmpFile1 lines: Hello World!
Size of dir: 304 bytes.
fileToWrite1 lines: Written with FileUtils!
fileToWrite2 lines: Written with FileUtils!
fileToWrite2 lines: For Java Code Geeks.