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  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, ...


  Difference between ConcurrentHashMap and Hashtable

Both ConcurrentHashMap and Hashtable are Collection classes for storing key value pairs and they both provide fast element search with a supplied key. They have much in common. However, we will not discuss the similarities between them here, instead we will focus on the differences between them. ConcurrentHashMap and Hashtable are both thread safe. But the mechanism for thread safe is different between them. Hashtable is synchronized, it utilizes the synchronization mechanism; while ConcurrentHa...


  Android socket programming example

Socket is a kind of interface for different sides t communicate, it usually identified by an IP and a port. There are many server side software on a server and they would provide different service. Each server many create some sockets and bind them to some ports so that clients can listen to. Software on the Internet will exchange data though a bidirectional connection established. Each end of the connection has a socket created. In Java, Socket and ServerSocket are in package, ServerSo...

35,617 3          JAVA ANDROID SOCKET

  Use cases of Java enumeration

JDK 1.5 introduces a new type -- enumeration. In Java, it's just a small feature, but it can bring us much convenience.Here we summarize some use cases of Java enumeration. 1. Constant Prior to JDK 1.5, we can define constant as public static final..., now we can use enumeration to group all constants in one enum variable and it also provides some useful functions. public enum Color {     RED, GREEN, BLANK, YELLOW   }  2.In Swit...

2,987 0          JAVA ENUMERATION ENUM

  30 minutes to fix Java vulnerability

On September 25, Adam Gowdiak from the Polish security consulting firm Security Explorations submitted a Java security vulnerability to Oracle and provided a proof-of-concept. The vulnerability exists in Java 5 6,7, once the user accesses hosted malware site, an attacker can remotely control the infected machine.Gowdiak later got in touch again with Oracle and got the response that the fix has reached the final stage. He can expect the patch in four months later. He eventually unbearable Oracle'...


  Writing Java codes conforming to coding standard

Recently, I was doing some cleanup to one of my current Java project. I find there are many codes which are not conforming to the Java coding standard. So I list them here and hope that people can improve your codes and write maintainable codes. Format source code and manage imports in Eclipse Eclipse provides functions of auto-formatting and imports management, you can use following shortcuts to use these functions. Ctrl+Shift+F --> Format source code Ctrl+Shift+O -- Manage imports an...


  3 ways to remove duplicates in List

Frequently, we may have an ArrayList which stores many values, and we need to process the ArrayList and get what are the distinct values in the list, or we may want to count occurrence of each value in the ArrayList. We can remove the duplicates in a few ways. Here we propose 3 methods :     public static void main(String[] args){        //SuperClass sub=new SubClass();                String[...


  How many Java programmers are there in the world?

Oracle says its 9,000,000, Wikipedia says its 10 million, 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...