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转载 java encapsulation

Encapsulation in Java is a mechanism of wrapping the data (variables) and code acting on the data (methods) together as as single unit. In encapsulation the variables of a class will be hidden from ot

2016-02-18 12:14:18 487

原创 OSI 7 layers model

The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard

2016-02-12 10:07:57 677

原创 http VS https

What are they: HTTP, or hypertext transfer protocol, is the way a Web server communicates with browsers like Internet Explorer® and Mozilla Firefox®. HTTP lets visitors view a site and send informa

2016-02-12 09:58:27 394

原创 SQL primary key, foreign key

PRIMARY KEY 是为了保证数据的完整性 FOREIGN KEY 是为了保证数据引用的完整性 The PRIMARY KEY constraint uniquely identifies each record in a database table. CREATE TABLE Persons ( Id_P int NOT NULL, LastName varchar(25

2016-02-12 09:45:53 585

转载 polymorphism

Polymorphism is the ability of an object to take on many forms. 多态是同一个行为具有多个不同表现形式或形态的能力. Any Java object that can pass more than one IS-A test is considered to bepolymorphic. There are

2016-02-12 09:23:20 463

转载 difference between abstract class and interface

interface Door{ void open(); void close(); } similarity: 1, 都是表示抽象的概念,不能直接定义一个object

2016-02-12 09:14:35 425

转载 join operations in SQL

Suppose there are two tables A and B. And there are: Aid Aname Bid Bname -- ---- -- ---- 1 Pirate 1 Rutabaga 2 Monkey 2 Pirate 3 Ninja

2016-02-12 05:21:58 303

转载 BloomFilter——大规模数据处理利器

Bloom Filter是由Bloom在1970年提出的一种多哈希函数映射的快速查找算法。通常应用在一些需要快速判断某个元素是否属于集合，但是并不严格要求100%正确的场合。一. 实例　　为了说明Bloom Filter存在的重要意义，举一个实例：　　假设要你写一个网络蜘蛛（web crawler）。由于网络间的链接错综复杂，蜘蛛在网络间爬行很可能会形成“环”。

2016-02-09 11:30:58 375

原创 C++ 输入输出

1 如何判断按回车键后即输入结束？使用 while(cin >> a)，例如：int number; while(cin >> number){ ... }

2013-11-27 04:09:52 362

转载 C语言：存取结构体成员的点运算符(.)和箭头运算符(->)的区别（转）

相同点：两个都是二元操作符，其右操作符是成员的名称。不同点：点操作符左边的操作数是一个“结果为结构”的表达式；箭头操作符左边的操作数是一个指向结构的指针。例如： struct AAA { int a; char b; }; struct AAA q; 访问成员就用：q.a; struct AAA *

2013-11-26 00:14:50 1045

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