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  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

  What kind of automated testing does Facebook do?

We do several kinds of testing. Some specifics:For our PHP code, we have a suite of a few thousand test classes using the PHPUnit framework. They range in complexity from simple true unit tests to large-scale integration tests that hit our production backend services. The PHPUnit tests are run both by developers as part of their workflow and continuously by an automated test runner on dedicated hardware. Our developer tools automatically use code coverage data to run tests that cover the ...

   Facebook,Testing,PHP,Automated testing     2012-02-28 08:10:10

  Oracle released an urgent Java patch

On March 23, Oracle just released an urgent Java patch which is out of its normal update schedule. The security vulnerability is related to the Java SE running in web browsers on desktops. The CVE ID for this issue is CVE-2016-0636. With the unpatched Java, attackers can remotely exploit the target system without username and credentials. Successful exploits can impact the availability, integrity, and confidentiality of the user's system. When the user access pages containing malicious code...

   JAVA,SECURITY,ORACLE,NEWS     2016-03-25 08:39:59

  Hexadecimal and long in Java

Today I encountered a hexadecimal operation problem when I was implementing a bit reverse function for integer type. Basically in the implementation, there is an operation which is to do the bit operation & between one long integer and a hexadecimal number 0x00000000FFFFFFFFF. I was expecting that the high 32 bits of the long integer will be zeroed. But unfortunately I didn't get the expected result. The basic implementation is: long num=0x00F0_0000; num = (num>>16) | (num<<16); ...

   Hexadecimal,long,Java,bitwise operation     2014-06-18 23:44:32

  How to write good requirements

Requirements are pretty ubiquitous in the embedded world. They are used to define tasks, help coordinate large development efforts, and to communicate the behavior of the desired end product between the developers and the customer. When done right, requirements can be very useful. Unfortunately, if you spend much time working in the embedded world you quickly discover that there are a lot of bad requirements. And then when you try to go fix them, you quickly discover that writing good req...

   Requirement gathering,Good requirement     2012-02-18 12:53:15

  How Kafka achieves high throughput low latency

Kafka is a message streaming system with high throughput and low latency. It is widely adopted in lots of big companies. A well configured Kafka cluster can achieve super high throughput with millions of concurrent writes. How Kafka can achieve this? This post will try to explain some technologies used by Kafka. Page cache + Disk sequential write Every time when Kafka receives a record, it will write it to disk file eventually. But if it writes to disk every time it receives a record, it would ...

   BIG DATA,KAFKA     2019-03-08 09:42:57

  Mount DD image on Linux

Yesterday, my Raspberry Pi running Arch Linux was not able to boot with error: Kernel Panic, not syncing: no init found. I spent a night on it, but could not find a working solution. The last option is easy: reinstall the system. That is really the last resort, for I do not want to re-setup everything I have done: samba server, Time Machine server, Xunlei Offline Downloader… Unable to mount the SD card The system does not boot, so I need to find a way to get into the file system to identi...

   LINUX,DD IMAGE     2014-06-24 07:49:14

  Android 4.0+ occupies quarter of Android market

Google updates its developer page about Android platform version market share. From the latest data, we can find Android 4.0 and above system occupy around 25% of all Android market. But Android 2.3 Gingerbread still occupies over 50% of Android market. From the above chart, Android 4.0 has 23.7% market share, the latest Android 4.1 JellyBean takes 1.8%, these two have 25.5% market share in total. But Android 2.3 Gingerbread alone still dominates the Android market, it takes 55.8% market share....

   Google,Android,Share     2012-10-02 19:22:19

  Check file readability in Java

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, ...

   Java,Files,Readable,Check     2013-12-05 06:10:15

  Use Java ThreadLocal with caution

According to Oracle documentation, ThreadLocal is a class provides thread-local variables. These variables differ from their normal counterparts in that each thread that accesses one (via its get or set method) has its own, independently initialized copy of the variable. ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread. In short, ThreadLocal variables are variables belong to a thread, not a class or an instance of a class. One common...

   JAVA,MEMORY LEAK, THREADLOCAL     2015-11-03 07:31:57

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