FilenameFilter学习

迷南。 2022-08-06 14:18 170阅读 0赞

从给定的一个路径中筛选中某种格式的文件，通常的做法，便是遍历该目录，然后按照文件后缀来判断该文件是否符合判断条件。

其实 java的File 类有一个自带的过滤方法，即FilenameFilter接口

FilenameFilter接口自带一个accept方法，过滤符合条件的文件类型

package java.io;
    
    /**
     * Instances of classes that implement this interface are used to
     * filter filenames. These instances are used to filter directory
     * listings in the <code>list</code> method of class
     * <code>File</code>, and by the Abstract Window Toolkit's file
     * dialog component.
     *
     * @author  Arthur van Hoff
     * @author  Jonathan Payne
     * @see     java.awt.FileDialog#setFilenameFilter(java.io.FilenameFilter)
     * @see     java.io.File
     * @see     java.io.File#list(java.io.FilenameFilter)
     * @since   JDK1.0
     */
    public interface FilenameFilter {
        /**
         * Tests if a specified file should be included in a file list.
         *
         * @param   dir    the directory in which the file was found.
         * @param   name   the name of the file.
         * @return  <code>true</code> if and only if the name should be
         * included in the file list; <code>false</code> otherwise.
         */
        boolean accept(File dir, String name);
    }

FilenameFilter 接口中的accept方法，主要判断给定的文件是否包含在该目录中

通过FilenameFilter 接口改造后的代码

public class FileFilter {
    
    	public static void main(String[] args) {
    		File filepath = new File("F:\\论文\\中国知网论文\\中国知网论文");
    		List<File> list = filterFile(filepath);
    		System.out.println(list.size());
    	}
    	
    	public static List<File> filterFile(File file) {
    		// 定义变量list来接收最后的文件列表
    		List<File> list = new ArrayList<File>();
    		
    		// 将文件类型给到FilterName 中
    		FilterName filter = new FilterName(".abcd"); 
    		
    		// 文件过滤
            String[] files = file.list(filter);  
            
            // 由于File.list(FilenameFilter filter) 返回结果为数组
            // 此处将数组转换为list
            if (null != files) {
                for (String fileName : files) {
                	list.add(new File(fileName));
                }
            }
    		
    		return list;
    	}
    }
    
    class FilterName implements FilenameFilter {
        
    	private String type;
        
    	// 构造方法，定义要过滤的文件类型
        FilterName(String type) {
        	this.type = type;
        }
        
    	@Override
    	public boolean accept(File dir, String name) {
    		return name.endsWith(type);
    	}
    }