A security manager is an object that is used to check whether the operation we want to perform is not violating the security policy of the operating system.
Sometimes we want to perform any operation and get an exception
Exception in thread "AWT-EventQueue-1" java.security.AccessControlException: access denied (java.io.FilePermission characteroutput.txt write) at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323) at java.security.AccessController.checkPermission(AccessController.java:546) at java.lang.SecurityManager.checkPermission(SecurityManager.java:532) at java.lang.SecurityManager.checkWrite(SecurityManager.java:962) at java.io.FileOutputStream.<init>(FileOutputStream.java:169) at java.io.FileOutputStream.<init>(FileOutputStream.java:70) at java.io.FileWriter.<init>(FileWriter.java:46)
The security manager is an object of the type
SecurityManager to obtain a reference to this object, invoke.
SecurityManager appsm = System.getSecurityManager();
If there is no security manager, this method returns.
The SecurityManager class defines many other methods used to verify other kinds of operations. For example,
SecurityManager.checkAccess verifies thread accesses, and verifies
SecurityManager.checkPropertyAccess access to the specified property. Each operation or group of operations has its own
In addition, the set of methods
checkXXX() represents the set of operations that are already subject to the protection of the security manager. Typically, an application does not have to directly invoke any methods