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  Access control in Java -- doPrivileged

Previously we have introduced how Java performs permission check to protect resource access. What if sometimes we need to give some class the temporary access to some resource which it initially doesn't have? AccessController provides six doPrivileged methods to fulfill this requirement. These six methods have below signatures : static T doPrivileged(PrivilegedAction action)static T doPrivileged(PrivilegedAction action, AccessControlContext context)static T doPrivileged(PrivilegedExceptionA...

   JAVA,SECURITY,DOPRIVILEGED     2016-03-08 05:46:42

  Set file permission in Java

Prior to Java 6,  there is no good solution at the Java level to provide file permission management. You need to implement your own native methods or call the Runtime.exec() to invoke the system routine such as chmod in LInux. Since Java 6, Java introduces a set of methods which can be used to set the file permission at Java level. These methods include: File.setReadable(boolean); File.setWritable(boolean); FIle.setExecutable(boolean); File.setReadable(boolean, boolean); File.setWritable(bo...

   JAVA, FILE PERMISSION, POSIX,learnjava     2015-08-29 03:37:37

  How to Ace a Google Interview

Imagine a man named Jim. He's applying for a job at Google. Jim knows that the odds are stacked against him. Google receives a million job applications a year. It's estimated that only about 1 in 130 applications results in a job. By comparison, about 1 in 14 high-school students applying to Harvard gets accepted. Jim's first interviewer is late and sweaty: He's biked to work. He starts with some polite questions about Jim's work history. Jim eagerly explains his short career. The intervi...

   Google,Interview,Questions and answers,Job     2011-12-26 09:17:36

  Generate certificate in Java -- Certificate chain

In previous post, we have introduced the use of Certificate and how to generate self signed certificate using Java. In this post, we will show you how to generate a certificate chain. Sometimes we may only have a certificate request or we don't have a trusted certificate which can be used for business. Now we need to have a trusted CA to sign our certificate so that it can be used on SSL communications. To generate a certificate chain, we may first have our own certificate(A), then we may use ot...

   Java,Certificate chain,Creation, Pure Java     2014-07-30 08:24:52

  Singleton Design Pattern in Java

Singleton is frequently used in applications where resource may be expensive to create and no instance specific state needs to be maintained. For example, when creating database connection, a singleton may be needed. Today we will share the famous Singleton design pattern in Java. 1. Definition Singleton design pattern is a design pattern that restricts the instantiation of a class to one object. It is one of the most well-known design patterns. 2. Application Singleton ...

   DESIGN PATTERN,SINGLETON,MULTITHREAD,JAVA     2020-04-11 02:16:28

  Generating CSR using Java

A CSR(Certificate Signing Request) is a kind of request generated by an application and is to be sent to a Certificate Authority to create a signed certificate which can be distributed. It usually contains certificate information such as subject name, public key info and signature info. In Java, keytool can be used to generate a certificate request with option -certreq.  But sometimes if an application wants to create a CSR programmatically, keytool will not do a favor, instead you should u...

   JAVA,SECURITY,CSR,CERTIFICATE REQUEST     2016-05-25 04:49:17

  Recursive class initialization in Java

When a Java class is referenced and initialized, it has to go through the loading and linking first. Once the loading and linking complete successfully. The class will be initialized. The static variables and constant variables will be initialized during this process. Once the class is initialized, it is ready for use. If when class A is initialized and it is referencing a class B, the class B will also get initialized. But what will happen if class B is referencing class A as well? This is call...

   Java,JVM,class initialization,static final     2015-04-15 21:04:29

  Apple CEO criticizes Windows 8 on D10

In the D10 Digital Conference held by The Wall Street Journal, Apple’s CEO Tim Cook expressed his sharp criticism about Windows 8 to be launched by Microsoft. According to Cook, the idea of this OS attempting to perfectly apply to both tablet and PC is far from realistic.On D10, Tim Cook said : "[With Windows 8, Microsoft] is pulling all of the leg weight of the PC market. You wind up with something that's very similar to what tablets were 10 years ago. The more you look at combining th...

   Apple CEO,Tim Cook,Windows 8,D10     2012-05-31 05:31:32

  Tomcat vs. Apache: Why One Over the Other?

When determining which type of web server to use, the differences and technical details can be daunting. It can be a difficult task to compare web servers and make the decision on which is best for you and your project. Since Apache is currently the most popular web server, this article will discuss the differences between the Apache Web Server and Apache Tomcat, which are very different and fulfill different needs.The Apache Web Server, often just called “Apache” or â€...

   Apache,Tomcat,Choice,Web server     2012-03-23 12:01:25

  Java Cipher encryption/decryption example

In Java, Cipher is the API for doing data encryption/decryption. Many cryptographic algorithms such as AES, DES, RC4 etc can be specified when creating Cipher instance. The Cipher instance calls the underlying algorithm specific implementation to do the actual encryption/decryption.  Before doing the encryption/decryption, a key needs to be created and it will be used to do the encryption/decryption. A sample program for performing all these is : import java.security.Key; import javax.cryp...

   Java, Java Security, Cipher, Example, Sample     2015-08-14 07:07:10

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