Introduction:
java.io.FileNameFilter is a interface which is for filtering by filename, if filename can meet the standard we set,return list of files.
usages:
creating a class and implementing the interface of FileNameFilter,what you gonna do is override the public function of accept.
Details of accept function:
boolean accept(File dir, String name);
Accept is a callback function,and first invoke is in the following functions.
(1)String []fs = f.list(FilenameFilter filter);
(2)File[]fs = f.listFiles(FilenameFilter filter);
public String[] list(FilenameFilter filter) {
String names[] = list();
if ((names == null) || (filter == null)) {
return names;
}
List<String> v = new ArrayList<>();
for (int i = 0 ; i < names.length ; i++) {
if (filter.accept(this, names[i])) {
v.add(names[i]);
}
}
return v.toArray(new String[v.size()]);
}
public File[] listFiles(FilenameFilter filter) {
String ss[] = list();
if (ss == null) return null;
ArrayList<File> files = new ArrayList<>();
for (String s : ss)
if ((filter == null) || filter.accept(this, s))
files.add(new File(s, this));
return files.toArray(new File[files.size()]);
}
Example:
public class Demo2 {
public static void main(String[] args) {
File f = new File("C:/Users/caich5/Desktop/Chris/note");
MyFilter filter = new MyFilter(".txt"); String[] files = f.list(filter);
for(String a:files){
System.out.println(a);
}
}
static class MyFilter implements FilenameFilter{
private String type;
public MyFilter(String type){
this.type = type;
}
public boolean accept(File f,String name){
return name.endsWith(type);
}
}
}