SEARCH KEYWORD -- METHOD PARAMETER
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
A C++ program puzzle
Recently I came across a question asked by wang2191195 on a Chinese IT forum CSDN which asks about a C++ program puzzle. He has a code snippet which cannot be compiled. The code is:#include <cstdlib> #include <iostream> using namespace std; class Base{ public: virtual void func(){ cout << "Base::func()" << endl; } virtual int func( int num ){ cout << "Base::func( int " << num << " )" << endl; return 0; ...
Do NOT use boolean variable as function parameters
We follow lots of coding styles and coding standards when we do programming, but we may frequently forget one. The forgotten one is that do not use boolean parameter as the function parameters. The reason is it would greatly reduce the readability of the code. Don't believe it? When you read the following code, what does this code mean? widget->repaint(false); Do not repaint? Or what does this mean? After looking at the document, we know that this parameter is whether ...
CODING STYLE,BOOLEAN,FUNCTION PARAMETER,CODING STANDARD,METHOD PARAMETER 2012-04-22 02:38:45
Solution to getKeyCode() returns 0 in Java
The getKeyChar method always returns a valid Unicode character or CHAR_UNDEFINED. Character input is reported by KEY_TYPED events: KEY_PRESSED and KEY_RELEASED events are not necessarily associated with character input. Therefore, the result of the getKeyChar method is guaranteed to be meaningful only for KEY_TYPED events.For key pressed and key released events, the getKeyCode method returns the event's keyCode. For key typed events, the getKeyCode method always returns VK_UNDEFINED....
Java,KeyCode,0,KeyListener 2011-06-06 10:38:11
Break down defer statements in GoLang
Basic Concepts What are the characteristics of the deferred statement defer in Go language? When is it usually used? The deferred statement(defer statement) in Go language has the following characteristics: Deferred Execution: Deferred statements are executed before the function containing them exits, regardless of whether the function returns normally or encounters an exception. Last In, First Out (LIFO): If there are multiple deferred statements, they are executed in the order of last in, f...
Turn on SecurityManager in Java
SecurityManager in Java is to check whether the application codes can access some restricted resource such as file, socket etc. This can be used in applications which have high security requirements. With this feature turned on, our system resources can be secured with only permitted operations. When JVM starts, it will first check whether the SecurityManager is on by checking the system property java.security.manager, if it's on, then an instance of SecurityManager will be created and it can be...
SecurityManager,enable,program 2013-12-16 05:03:53
Traditional recursion vs Tail recursion
Recursion is a frequently adopted pattern for solving some sort of algorithm problems which need to divide and conquer a big issue and solve the smaller but the same issue first. For example, calculating fibonacci accumulating sum and calculating factorials. In these kinds of issues, recursion is more straightforward than their loop counterpart. Furthermore, recursion may need less code and looks more concise. For example, let's calculate sum of a set of numbers starting with 0 and st...
ALGORITHM,RECURSION,TAIL RECURSION,TRADITIONAL RECURSION 2016-09-23 23:54:09
A trap about PHP random number
The method to get random number in PHP is very simple, we only need to use rand() function. int rand ( int $min , int $max ) One function call can return the random number in a specified range. But in fact, the random number in computer is actually pseudorandomness, generally to increase the randomness, we may set a random seed before calling rand(). void srand ([ int $seed ] ) According to other language features, we should pass a time value as a parameter to the srand() function, generally...
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[...
A trap in PDOStatement::bindParam
First, let's check out below codes: <?php $dbh = new PDO('mysql:host=localhost;dbname=test', "test"); $query = <<prepare($query); $bind_params = array(':username' => "laruence", ':password' => "weibo"); foreach( $bind_params as $key => $value ){ $statement->bindParam($key, $value); } $statement->execute(); What is the SQL executed finally? Is there any problem with above codes? Many people may think the query executed is : INSERT INTO `user` (`username`, `password...
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