File operation is quite platform dependent. Although Java is a cross platform programming language, the file operation in Java is also platform dependent. The obvious evidence is the file permission check. In Java, we can call canRead(), canWrite() and canExecutable() to check whether the program can read, write or execute the file specified. However, on Windows, when we call canRead() on a File object, we may get unexpected result.Actually, on Windows, when we call canRead() on a File object, we will always get the true returned even if we have denied the read access to the file. There is als...

Windows-MY is a type of keystore on Windows which is managed by the Windows operating system. It stores the user keys and certificates which can be used to perform cryptographic operations such as signature verification, data encryption etc. Since it's a kind of native keystore, Java doesn't have a general API to access it.To help Java applications access the keys and certificates stored in Windows-MY keystore, Java provides a separate API -- SunMSCAPI. The SunMSCAPI provider is layered on top of CAPI and helps Java platform applications access CAPI cryptographic services using ...

BKS is a keystore format provided by the popular third party Java cryptographic library provider -- BouncyCastle. It is a keystore similar to the JKS provided by Oracle JDK. Before starting to use BKS, the BouncyCastle provider has to be downloaded and installed. To download the provider, please go to BouncyCastle download page. The provider can be installed by adding an entry in the java.security file.security.provider.N=org.bouncycastle.jce.provider.BouncyCastleProviderN means the provider index in the provider list.Creating BKS keystoreTo create a BKS keystore, you just need to create ...

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.crypto.Cipher;import javax.crypto.KeyGenerator;public class CipherSample { public static void main(String[] ...

Object class has a protected clone() method declared to make it possible for all classes make a clone of itself when needed. The clone() is often used when a new instance of the class is needed while at the same time to maintain the same state as the original object. Any class which wants to have clone enabled has to implement the marker interface Cloneable.If a class which implements Cloneable doesn't override the Object.clone() method, the Object.clone() method will be called to just make a binary copy of the original, which amounts to a shallow clone, with all the referenced objects staying...

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(boolean, boolean);FIle.setExecutable(boolean, boolean);Here File.setReadable(boolean, true) is the same as ...

Normally after installing Java, there will be an association between .jar and the javaw.exe. This enables the executable jar to be opened on double click. You can check the association by going to Control Panel -> Programs -> Default Programs -> Associate a file type or protocol with a program.The default program of a file type can be changed in this dialog. However sometimes there are cases where the file association for .jar may be altered after a third party application installed. The executable jar may not be able to be started normally post that and it still doesn't work eve...

When writing code using native library in Java, normally the first step is loading some native library.static{　　System.load("D:" + File.separator + "Hello.dll");}JDK provides two ways to load libraries:System.load(String filename)System.loadLibrary(String libname)This post will try to explain the differences of these two ways.According to Java Doc on System.load(), it has below description.Loads the native library specified by the filename argument. The filename argument must be an absolute path name.The parameter of this method should be an absolute file path with the exten...