使用FileUtils时只能迭代数组或java.lang.Iterable的实例

Question

I am trying to delete a particular folder in Java and I am using Apache Commons class to do the job. If there is any better option please let me know as well.

import org.apache.commons.io.FileUtils;

FileUtils.deleteDirectory(new File(destination));

Now what I need to do is - I need to find all the directories within this folder /opt/hello/world which is X days old (here X can be 30 days) and delete all those directory one by one. These directories can contain files as well so once I delete directory, files will also get deleted . I was looking into the API and I saw AgeFilter class so I started using like this:

import java.io.File;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.filefilter.AgeFileFilter;

private static final int DAYS_OLD = 30;

public void deleteFiles(File file) {
    long purgeTime = System.currentTimeMillis() - (DAYS_OLD * 24L * 60L * 60L * 1000L);
    Iterator<File> filesToDelete = FileUtils.iterateFiles(file, new AgeFileFilter(purgeTime), TRUE);
    for (File aFile : filesToDelete) {
        aFile.delete();
    }
}

But I am getting this error in for loop. What wrong I am doing?

Can only iterate over an array or an instance of java.lang.Iterable

Update:-

long purgeTime = System.currentTimeMillis() - (DAYS_OLD * 24L * 60L * 60L * 1000L);
AgeFileFilter filter = new AgeFileFilter(purgeTime);

File path = new File("/opt/hello/world");
File[] oldFolders = FileFilterUtils.filter(filter, path);

for (File folder : oldFolders) {
    FileUtils.deleteDirectory(folder);
}

Answer 1

You could use FileFilterUtils.filter(IOFileFilter, File...) instead, which will return a array of File s matching your filter.

I'd also recommend using just about anything else then basic time arithmetic, for example Java 8 has a new Time API, you could use a Joda-Time or even Calendar at a stretch, they will account for some of the anomalies surrounding date/time computation

As an example...

LocalDate today = LocalDate.now();
LocalDate eailer = today.minusDays(30);

Date threshold = Date.from(eailer.atStartOfDay(ZoneId.systemDefault()).toInstant());
AgeFileFilter filter = new AgeFileFilter(threshold);

File path = new File("...");
File[] oldFolders = FileFilterUtils.filter(
                FileFilterUtils.directoryFileFilter(), 
                FileFilterUtils.filter(
                                filter, 
                                path.listFiles()));

for (File folder : oldFolders) {
    System.out.println(folder);
}

But which you would use ( Iterable or array) comes down to what you need

Answer 2

You're facing the same problem of this guy

To safely remove from a collection while iterating over it you should use an Iterator.

**And call the next item before delete

Mark answered in a complete way. Take a look here

 List<File> files= .... Iterator<File> i = files.iterator(); while (i.hasNext()) { File s = i.next(); // must be called before you can call i.remove() // Do something i.remove(); }