26file filter anonymous inner class and lambda optimization

practice ：
  Traverse and print multi-level directories , Traverse C：abc Folder , namely abc The subfolders of the folder , as long as .java Final document
C:\abc
C:\abc\a
C:\abc\a\a.java
C:\abc\a\a.txt
C:\abc\abc.java
C:\abc\abc.txt
C:\abc\b
C:\abc\b\b.java
C:\abc\b\b.txt

package demo26file Filter anonymous inner class ;
/*
 practice ：
  Traverse and print multi-level directories , Traverse C：abc Folder , namely abc The subfolders of the folder , as long as .java Final document 
C:\abc
C:\abc\a
C:\abc\a\a.java
C:\abc\a\a.txt
C:\abc\abc.java
C:\abc\abc.txt
C:\abc\b
C:\abc\b\b.java
C:\abc\b\b.txt
 We can use filters to optimize ：
 stay File There are two and... In the class listFiles Overloaded method , What method parameters pass is a filter 
  File[] listFiles(FileFilter filter)  java.io.FileFilter Interface ： Used for abstract pathnames （File object ） Filter 
      effect ： For filtering files （File object ）
      Abstract method ： Method for passing files   boolean accept(File pathname)  Test whether the specified Abstract path name should be included in a path list 
         Parameters ：File pathname： Use ListFiles Method to traverse the directory , Every file object obtained 
  File[] listFiles(FilenameFilter filter)   java.io.FilenameFilter Interface ; Class instances that implement this interface can be used to filter file names 
      effect ： Used to filter abstract names 
      Abstract method ： Methods for filtering Abstract files   boolean accept(File dir,String name)   Test whether the specified folder should be included in a file list 
          Parameters ：File dir： The traversed directory passed in the constructor 
               String name： Use listFiles Method to traverse the directory , Get the name of each file or folder 

 Be careful ： The two filter interfaces do not implement classes , We need to write implementation classes , Rewrite the filtering rules 

 */
import demo25file filter .FileFiletermpl;

import java.io.File;
import java.io.FileFilter;
import java.io.FilenameFilter;

public class DemoRecurison {
    public static void main(String[] args) {
        File file=new File("C:\\abc");
        getAllFile(file);
    }
    private static void getAllFile(File dir){
        //System.out.println(dir);// Print the name of the traversed Directory 
      /*  File[] files=dir.listFiles(new FileFilter() {
            @Override
            public boolean accept(File pathname) {
                // Filtering rules ,pathname It's a document , Or is it .java The end of the file returns true
                return pathname.isDirectory() || pathname.getName().toLowerCase().endsWith(".java");
            }
        });// Pass filter object 
        // Use Lamdba Expression optimization anonymous inner class 
        File[] file=dir.listFiles((File pathname)->{
            // Filtering rules ,pathname It's a document , Or is it .java The end of the file returns true
            return pathname.isDirectory() || pathname.getName().toLowerCase().endsWith(".java");
        });*/
        /*
        listFiles The method is done in total 3 thing ：
        1.listFiles Method will traverse the directory passed in the constructor , Get every file in the directory / Folder -- Encapsulated in the File object 
        2.listFiles Method will call accept Method 
        3.listFiles Method will traverse every File object , Pass to accept Method parameters pathname

        accept Method returns a Boolean value ,true Will pass the past object （ Folder 、.java Final document ） Save to Files Array   false You won't pass on the past File Object is saved in the array 
         */



       /* File[] files=dir.listFiles(new FilenameFilter() {
            @Override
            public boolean accept(File dir, String name) {
                 // Filtering rules ,pathname It's a document , Or is it .java The end of the file returns true
                return  new File(dir,name).isDirectory() || name.toLowerCase().endsWith(".java");
                // File(dir,name).isDirectory() Combine file objects according to directories 
            }
        });*/

       // Use Lamdba Expression optimization anonymous inner class （ There is only one abstract method in the interface ）
        File[] file=dir.listFiles((File d, String name)->{
            return  new File(d,name).isDirectory() || name.toLowerCase().endsWith(".java");
            // File(dir,name).isDirectory() Combine file objects according to directories 
        });





        for (File f:file){
           if (f.isDirectory()){//f It's a folder , Then traverse the entire folder 
               getAllFile(f);// Recursively call itself 
           }else{
               System.out.println(f);
           }
        }
    }
}

result ：