import wildcard, import specific class and class search order
Today, I got a problem compiling a java source code. The source code uses several classes in another package so I use “import fruit.*” to try to import all classes […]
public, private, package, protected in Java
In Java, class members can be declared with public, private, protected, or nothing. If you need to access a member from another package (even from a derived class)using obj.membername, the […]
difference between protected in C++ and protected in Java
In C++, protected members cannot be accessed outside the class and its derived classes using obj.membername #include <QtCore> //#include “windows.h” //#include <QApplication> class A { public: void fun() { qDebug()<<“a”; […]
public,private,protected in C++
When talking about public,private, and protected in C++, two words must pop up in your head:accessibility and visibility. Unfortunately, the two academic words are just created to confuse learners as […]
java compile and execution
Let’s compile a simple java program in current directory(javac Test.java): //Test.java class Test { String a=”hello”; public static void main(String[]args) { Test b=new Test(); b.a=”world”; System.out.println(b.a); App app=new App(); app.fun(); […]
How to center a button using CSS?
Button is an inline element. It can not be centered using the “margin:auto;” that is for block element. Even if you set “display:inline-block” for it, the “margin:auto;” still has no […]
The default height and width of empty div in CSS
The height and width CSS properties are not inheritable. If not specified, their default value is “auto” which means “browser will calculate it“. But how does the browser calculate the […]
the difference between px and em for font-size
The articles I’ve read that talk about px and em all say px is an absolute unit while em is a relative unit. “Absolute” seems easy to understand. That is […]
difference between javascript array and php array
I love php array because the array’s key can not only be number but also be string. $arr=array(“a”,”b”,”c”); $arr=[“a”,”b”,”c”]; $arr=array(“k1″=>”a”,”k2″=>”b”,”k3″=>”c”); $arr=[“k1″=>”a”,”k2″=>”b”,”k3″=>”c”]; That makes it an association array or a […]
The best way to use multiple-line string in javascript
Javascript does not allow multi -line string constant. var html=’ <div> <span> hello world</span> </div> ‘; alert(html); This will produce an error:”unterminated string literal“. To write multi-line string, you have […]