Java Java类

Java 中的 io.FilePermission 类

Java.io.FilePermission类用于表示对文件或目录的访问。这些访问采用路径名和与路径名关联的一组操作的形式（指定要打开的文件以及扩展名和路径）。

例如，在FilePermission(“GEEKS.txt”, “read”)中，“GEEKS.txt”是路径，“read”是正在执行的操作。

这些动作如下：

read ：对文件的读取权限
write ：对文件的写权限
delete ：通过调用 File.delete 删除文件的权限
readlink :读取链接权限
execute :执行权限

宣言：

public final class FilePermission
   extends Permission
      implements Serializable

构造函数：

FilePermission(String p, String a) : Creates a new file permission object with "a" action.

FilePermission 类的方法：

equals(Object FP_obj) : Java.io.FilePermission.equals(Object FP_obj)告诉两个（即用这个对象检查FP_obj 路径名和文件名）FilePermission 对象是否相等。
句法：

public boolean equals(Object FP_obj)
Parameters : 
FP_obj : the FilePermission object to be verified with this object
Returns :
true : if both the objects are equal else, false.
Exception : 
----------

执行：

// Java Program illustrating equals() method
  
import java.io.*;
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        boolean bool = false;
  
        // Creating new FilePermissions("Path", "action")
        FilePermission FP_obj1 = new FilePermission("GEEKS", "read");
        FilePermission FP_obj2 = new FilePermission("ABC", "write");
        FilePermission FP_obj3 = new FilePermission("GEEKS", "read");
  
        // Use of equals method 
        bool = FP_obj2.equals(FP_obj1);
        System.out.println("Whether FP_obj1 equals FP_obj2 : " + bool);
  
        bool = FP_obj2.equals(FP_obj3);
        System.out.println("Whether FP_obj2 equals FP_obj2 : " + bool);
  
        bool = FP_obj1.equals(FP_obj3);
        System.out.println("Whether FP_obj3 equals FP_obj1 : " + bool);
  
  
    }
}

输出：

Whether FP_obj1 equals FP_obj2 : false
Whether FP_obj2 equals FP_obj2 : false
Whether FP_obj3 equals FP_obj1 : true

getActions() : Java.io.FilePermission.getActions()告诉这个 FilePermission 对象的动作。如果对象有两个动作：删除和读取，则该方法将返回“读取，删除”。
在这种情况下，此方法返回“规范字符串”： read、write、execute、delete、readlink
句法：

public String getActions()
Parameters : 
----------
Returns :
canonical string : representing the actions associated with the object.
Exception : 
----------

执行：

// Java Program illustrating getActions() method
import java.io.*;
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // Creating new FilePermissions
        FilePermission FP_obj1 = new FilePermission("GEEKS", "read, delete, write");
        FilePermission FP_obj2 = new FilePermission("ABC", "write, read, execute");
        FilePermission FP_obj3 = new FilePermission("GEEKS", "delete, readlink, read");
  
        // Use of getActions() method 
        String str = FP_obj1.getActions();
        System.out.println("Actions with FP_obj1 : " + str);
  
        str = FP_obj2.getActions();
        System.out.println("Actions with FP_obj2 : " + str);
  
        str = FP_obj3.getActions();
        System.out.println("Actions with FP_obj3 : " + str);
  
    }
}

输出：

Actions with FP_obj1 : read,write,delete
Actions with FP_obj2 : read,write,execute
Actions with FP_obj3 : read,delete,readlink

hashCode() : Java.io.FilePermission.hashCode()返回参数 FilePermission 对象的哈希码
句法：

public int hashCode()
Parameters : 
--------
Returns :
hash code value for the argumented object
Exception : 
----------

执行：

// Java Program illustrating hashCode() method
  
import java.io.*;
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // Creating new FilePermissions
        FilePermission FP_obj1=new FilePermission("GEEKS", "read, delete, write");
  
        // Use of hashCode() method
  
        int i = FP_obj1.hashCode();
        System.out.println("hashCode value for FP_obj1 : " + i);
  
    }
}

输出：

hashCode value for FP_obj1 : 0

暗示(Permission arg) : Java.io.FilePermission.implies(Permission arg)告诉这个 FilePermision 是否有参数的 Permission。
句法：

public boolean implies(Permission arg)
Parameters : 
arg : Permission to be checked 
Returns :
true if the FilePermission object has the argumented Permission else, false
Exception : 
----------

执行：

// Java Program illustrating implies() method
  
import java.io.*;
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // Creating new FilePermissions
        FilePermission FP_obj1 = new FilePermission("GEEKS", "read");
        FilePermission FP_obj2 = new FilePermission("ABC", "write");
        FilePermission FP_obj3 = new FilePermission("GEEKS", "delete");
  
        // Use of implies() method
  
        boolean check = FP_obj1.implies(FP_obj2);
        System.out.println("Using implies() for FP_obj1 : " + check);
                  
  
        // Checked here with the same FilePermission object
        check = FP_obj2.implies(FP_obj2);
        System.out.println("Using implies() for FP_obj2 : " + check);
          
    }
}

输出：

Using implies() for FP_obj1 : false
Using implies() for FP_obj2 : true

newPermissionCollection() : Java.io.FilePermission.newPermissionCollection()创建具有 FilePermission 对象的 PermissionCollection 对象。
句法：

public PermissionCollection newPermissionCollection()
Parameters : 
arg : Permission to be checked 
Returns :
new PermissionCollection object having the FilePermission objects.
Exception : 
----------

执行：

// Java Program illustrating newPermissionCollection() method
  
import java.io.*;
import java.security.PermissionCollection;
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        // Creating new FilePermissions
        FilePermission FP_obj1 = new FilePermission("GEEKS.txt", "read");
          
        // Creating new PermissionCollection
        // Use of newPermissionCollection() 
        PermissionCollection FP = FP_obj1.newPermissionCollection();
          
        // Collecting the Permissions of FP_obj1 for FP
        FP.add(FP_obj1);
          
        boolean check = FP.implies(new FilePermission("GEEKS.txt", "read"));
        System.out.println("Is newPermissionCollection() working : " + check);
  
    }
}

输出：

Is newPermissionCollection() working : true