package test;

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

public class FileFilterTest implements FileFilter {
  
  
  private String extension;
  
  public FileFilterTest(String extension) {

    this.extension = extension;
  }
  /**
   * 
   */
  @Override
  public boolean accept(File pathname) {
      
    if(pathname.isDirectory()){
      return false;
    }
    
    String name = pathname.getName();
    int num = name.lastIndexOf(".");
    if(num == -1){
      return false;
    }
    if(name.length()-1 == num){
      return false;
    } else {
    
      return extension.equals(name.substring(num+1));
    }
  }
  
  
  public static void main(String[] args) {
    
    File path = new File("E:\\書籍\\java 編程");
    //獲得過濾對象
    FileFilterTest ft = new FileFilterTest("pdf");
    
    File[] files = path.listFiles(ft);
    
    for (int i = 0; i < files.length; i++) {
      System.out.println(files[i].getAbsolutePath());
    } 
    
  }

}

package test;

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

public class FileNameFilterTest implements FilenameFilter {
  
  //判斷圖片是否格式是否是 gif
  private boolean isGif(String fileName){
    if(fileName.toLowerCase().endsWith(".gif")){
      return true;
    } else {
      return false;
    }
    
  }
  //判斷圖片是否格式是否是 jpg
  private boolean isJpg(String fileName){
    if(fileName.toLowerCase().endsWith(".jpg")){
      return true;
    } else {
      return false;
    }
    
  }
  //判斷圖片是否格式是否是 png
  private boolean isPng(String fileName){
    if(fileName.toLowerCase().endsWith(".png")){
      return true;
    } else {
      return false;
    }
    
  }
  
  

  @Override
  public boolean accept(File dir, String name) {
    return (isGif(name)||isJpg(name)||isPng(name));
  }
  
  public static void main(String[] args) {
    File path = new File("C:\\img");
    //獲得過濾對象
    FileNameFilterTest ft = new FileNameFilterTest();
    
    File[] f = path.listFiles(ft);
    
    for (int i = 0; i < f.length; i++) {
      File file = f[i];
      
      System.out.println(file.getAbsolutePath());
      
    }
  }

}