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();    }}