Two different ways to implement an interface in java

By providing a concrete class

package com.mob;
import java.io.File;import java.io.FileFilter;
public class JavaFileFIlter implements FileFilter {

    @Override    public boolean accept (File file) {
        return file.getName().endsWith(".png");    }
}

This implements FileFilter which in this case is used to filter .png files

package com.mob;

import java.io.File;

public class FileFilterExample {

    public static void main (String[] args) {

        JavaFileFIlter javaFileFIlter = new JavaFileFIlter();

        File dir = new File("C:\\Madhu Personal");

        File[] files = dir.listFiles(javaFileFIlter);

        for (int i = 0; i< files.length; i++) {

            System.out.println(files[i].getName());

        }

    }

}

By writing an anonymous class

package com.mob;

import java.io.File;

import java.io.FileFilter;

public class FileFilterExample1 {

    public static void main (String[] args) {

        FileFilter fileFilter = new FileFilter() {

            @Override

            public boolean accept (File file) {

                return file.getName().endsWith(".png");

            }

        };

        File dir = new File("C:\\Madhu Personal");

        File[] files = dir.listFiles(fileFilter);

        for (int i = 0; i< files.length; i++) {

            System.out.println(files[i].getName());

        }

    }

}

Hope this helps:)