SEARCH KEYWORD -- ORACLE


  How many bytes a boolean value takes in Java?

Have you ever wondered how many bytes a boolean value takes in Java? One byte, this might be the answer comes out of your mind right away. But is it? Let's dig in more. Per Oracle documentation on boolean value definition, there is below statement: boolean: The boolean data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defin...

   JAVA,INTERVIEW,SIZE,BOOLEAN     2020-02-29 02:49:18

  How many Java programmers are there in the world?

Oracle says its 9,000,000, Wikipedia says its 10 million, NumberOf.net gives the exact number of Java programmers, 9007346.But how many Java programmers are there really? We cannot call everyone on the planet to ask whether he/she is a Java programmer or not.So we can only rely on some indirect methods to estimate, such as government statistics (There are around 43 million programmers in the world), TIOBE and Langpop, Employment portals, Eclipse and Tomcat download numbers.Download number of Ecl...

   Java programmer,number     2012-07-20 11:57:19

  A trick of building multithreaded application on Solaris

Firstly, Let’s see a simple multithreaded application: #include <stdio.h> #include <pthread.h> #include <errno.h> void *thread1_func(void *p_arg) { errno = 0; sleep(3); errno = 1; printf("%s exit, errno is %d\n", (char*)p_arg, errno); } void *thread2_func(void *p_arg) { errno = 0; sleep(5); printf("%s exit, errno is %d\n", (char*)p_arg, errno); } int main(void) { pthread_t t1, t2; ...

   C, Solaris     2014-10-14 02:59:40

  Arrays.equals() vs MessageDigest.isEqual()

Both Arrays.equals() and MessageDigest.isEqual() are used to compare the equality of two arrays. They can be interchangeably in many cases. However, they do have some differences which lead to different use cases in real applications. One difference is that the arrays passed to MessageDigest.isEqual() cannot be null while it's ok for Arrays.equals(). The one major difference between these two methods is that Arrays.equals() is not time-constant while MessageDigest.isEqual() is time-constant. Thi...

   Arrays.equal(),MessageDigest.isEqual(),Java,Security     2015-05-14 22:03:29

  A simple tutorial on writing Java native program

Java provides Java Native Interface(JNI) to enable developers to write programs which can utilize the underlying native libraries of the operating system. The benefits of writing native code are that they normally provide better performance compared to Java codes. Sometimes if you want to utilize some system specific functions you may also want to use JNI. One main drawback of writing native code is that your application may not be platform independent anymore. This is not what Java is desi...

   Java native interface, JNI, Native code, Sample     2015-08-15 08:28:15

  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

  Different types of keystore in Java -- PKCS11

PKCS11 keystore is designed for hardware storage modules（HSM）. It's an interface to talk to the HSMs. It doesn't actually store any keys but provide a set of classes to communicate with the underlying HSM. The actual keys and certificates are stored on the HSMs. The reason for storing the keys and materials is to ensure security and efficiency. Since the keys are on the HSMs, they are safe to be stolen. All encryption/decryption operations are performed on the HSMs as well, this incre...

   PKCS11,keystore,HSM,Java     2015-01-08 00:39:12

  Access control in Java -- Permission check order

Previously we showed you how to turn on SecurityManager in Java. After SecurityManager is turned on, a series of permission checks will be applied on the code you are calling in your application to protect some resources against malicious access such as files, sockets etc. To perform these permission checks, a set of Permissions will be created and checked using the AccessController. The AccessController has three purposes : To decide whether an access to a critical system resource is to be all...

   JAVA,SECURITY,ACCESSCONTROLLER     2016-03-07 04:17:40

  Java AbstractMethodError explained and demonstrated

According to Oracle Java API documentation, AbstractMethodError is a kind of runtime error where the application is having some incompatible changes which leads to a missing implementation of an abstract method. Below is the official description. Thrown when an application tries to call an abstract method. Normally, this error is caught by the compiler; this error can only occur at run time if the definition of some class has incompatibly changed since the currently executing method was last co...

   JAVA,ABSTRACTMETHODERROR     2016-07-22 22:03:20

  The difference between System.load and System.loadLibrary in Java

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 a...

   NATIVE,JNI,JAVA,SYSTEM.LOAD,SYSTEM.LOADLIBRARY     2019-02-05 05:49:28

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