Java read a file line by line – How Many Ways?

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Processing a text file line by line is a common thing programmers do. There are many related classes in the Java I/O package and this may get confusing. This post shows 4 different ways of reading a file line by line in Java. 1. FileInputStream and BufferedReader private static void readFile1(File fin) throws IOException { … Read more

Java: get a set of random numbers from a specified range

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This is a method that accepts a range (max) and a number (n), returns an array of n random numbers. n: size of random number array max: largest available number (exclusive) For example: Input: n=5, max=100 Output: an array containing 5 random numbers whose range is from 0 to 99. public static HashSet<Integer> getNRandom(int n, … Read more

Linux Process Programming – fork()

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What is a process?

In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system (OS), a process may be made up of multiple threads of execution that execute instructions concurrently.

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How Compiler Works?

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How compiler works is not easy to explain in one sentence. The best way is to use an example. A compiler is a computer program that transforms source code written in a high-level programming language into a lower level language. Basically, a compiler consists the following phases: Lexical Analysis, Syntax Analysis, Semantic Analysis, IR Generation, … Read more

Java Design Pattern: Observer

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In brief, Observer Pattern = publisher + subscriber. Observer pattern has been used in GUI action listener. Swing GUI example shows how action listener works like an observer. The following is a typical example about head hunter. There are two roles in this diagram – HeadHunter and JobSeeker. Job seekers subscribe to a head hunter, … Read more

An example of C++ dot vs. arrow usage

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vs. Overall, dot(.) is for object itself, arrow(->) is for pointer. A good example worth a thousand words. The following example should be a good one. #include <iostream>   using namespace std;   class Car { public: int number;   void Create() { cout << "Car created, number is: " << number << "\n" ; … Read more

Eclipse JDT tutorial: Parse a Java method by using ASTParser

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This tutorial belongs to Eclipse JDT Tutorial Series. ASTParser can use its setKind() method to set source to be parsed as a compilation unit, single expression, a sequence of statements, or a sequence of class body declarations. parser.setKind(ASTParser.K_COMPILATION_UNIT);parser.setKind(ASTParser.K_COMPILATION_UNIT); Any of those four can not handle a single independent method. This is not pleasant. Following the … Read more

Eclipse JDT Tutorials

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JDT is supported by 3 pillars: Java Model, Search Engine, and AST. It is a handy tool for manipulating Java source code. However, the handy tool comes with a steep learning curve even for an experienced Java developer and there are just not enough proper code examples. This page summarizes the code examples for using … Read more