毕向东_Java基础视频教程第20天_IO流（5~6）

第20天-05-IO流(文件列表一)

static File[] listRoots() 　　

　　List the available filesystem roots.

String[] list() 　　

　　Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname.

String[] list(FilenameFilter filter) 　　

　　Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.

File[] listFiles() 　　

　　Returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname.

File[] listFiles(FileFilter filter) 　　

　　Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.

File[] listFiles(FilenameFilter filter) 　　

　　Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.

package bxd;

import java.io.File;

public class FileDemo4 {
    public static void method_1() {
        File[] files = File.listRoots();
        for (File file : files) {
            System.out.println(file);
        }
    }

    public static void method_2() {
        File dir = new File("/Users/Eric/Desktop");
        // 如果File dir传入的不是目录而是文件, 则会抛出空指针异常
        for (String name : dir.list()) {
            System.out.println(name);
        }
    }

    public static void main(String[] args) {
        method_2();
    }
}

第20天-06-IO流(文件列表二)

package bxd;

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

public class FileDemo5 {
    public static void method_1() {
        File demoDir = new File("/Users/Eric/Desktop");
        String[] names = demoDir.list(new FilenameFilter() {
            @Override
            public boolean accept(File dir, String name) {    // accept方法的入参File dir即为File demoDir
                return name.endsWith(".pdf");
            }
        });

        for (String name : names) {
            System.out.println(name);
        }
    }

    public static void method_2() {
        File dir = new File("/Users/Eric/Desktop");
        for (File file : dir.listFiles()) {
            System.out.println(file.getName() + "::" + file.length());
        }
    }

    public static void main(String[] args) {
        method_2();
    }
}