JAVA IO：修改文件权限

在java中，文件的权限对于不同的操作系统有不同的权限。 java 处理一些通用的权限。

检查文件是否允许：

1. file.canExecute(); – return true, file is executable; false is not.
2. file.canWrite(); – return true, file is writable; false is not.
3. file.canRead(); – return true, file is readable; false is not.

设置文件权限：

1. file.setExecutable(boolean); – true, allow execute operations; false to disallow it.
2. file.setReadable(boolean); – true, allow read operations; false to disallow it.
3. file.setWritable(boolean); – true, allow write operations; false to disallow it.

在*nix系统中，你可能需要配置更加明确的文件权限，如设置某个文件的权限为777.但是，java IO类没有相关方法。不过可以使用以下workaround：

Runtime.getRuntime().exec("chmod 777 file");

查看和修改文件权限完整例子：

package org.hnrsc.io;

import java.io.File;
import java.io.IOException;

//
public class JavaFileIO {

    public static void main(String[] args) {
        try {
            String filename = "test1.txt";
            String finalfile = "";
            String workingDir = System.getProperty("user.dir");


            finalfile = workingDir + File.separator + filename;

            System.out.println("Final filepath: " + finalfile);

            File file = new File(finalfile);
            if (file.createNewFile()) {
                System.out.println("File is created!");
            } else {
                System.out.println("File already exists.");
            }
            if (file.exists()) {
                System.out.println("Is Execute allow : " + file.canExecute());
                System.out.println("Is Write allow : " + file.canWrite());
                System.out.println("Is Read allow : " + file.canRead());
            }

            file.setExecutable(false);
            file.setReadable(false);
            file.setWritable(false);

            System.out.println("Is Execute allow : " + file.canExecute());
            System.out.println("Is Write allow : " + file.canWrite());
            System.out.println("Is Read allow : " + file.canRead());

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

本程序执行结果有点让人疑惑，为何设置以下属性为false后，只有writable变为false了？

 file.setExecutable(false);
 file.setReadable(false);
 file.setWritable(false);

Final filepath: N:\eclipse\workspace\JavaIO\test1.txt
File already exists.
Is Execute allow : true
Is Write allow : true
Is Read allow : true
--------------------------
Is Execute allow : true
Is Write allow : false
Is Read allow : true