Java学习Day2——关于类的概述

一、昨天的实践：术语随机生成器

//术语生成器
public class PhraseOMatic
{
	public static void main(String[] args)
	{
		//创建三个词库
		String[] wordListOne = {"24/7", "multi-Tier","30,000 foot","B-to-B","win-win",
								"front-end","web-based","pervasive","smart","six-sigma","critical-path","dynamic"};
		String[] wordListTwo = {"empowered","sticky","value-added","oriented","centric","distributed","clustered",
								"branded","outside-the-box","positioned","networked","focussed","leveraged","aligned",
								"targeted","shared","cooperative","accelerated"};
		String[] wordListThree = {"process","tipping-point","solution","architecture","core competency","strategy",
								"mindshare","portal","space","vision","paradigm","mission"};
								
		//计算词库长度
		int oneLength = wordListOne.length;
		int twoLength = wordListTwo.length;
		int threeLength = wordListThree.length;
		
		//生成随机数
		int rand1 = (int)(Math.random() * oneLength); //Math.random():0~1
		int rand2 = (int)(Math.random() * twoLength);
		int rand3 = (int)(Math.random() * threeLength);

		//生成专家术语
		String phrase = wordListOne[rand1] + " " + wordListTwo[rand2] + " " +wordListThree[rand3];
		System.out.println("What we want is a " + phrase);
	}
}

运行结果：

二、类

概念

1. 类(class)：像一张蓝图，它定义了要使用什么样的数据以及怎么样使用这些数据。
2. 方法(method)：定义了一些操作，如何使用数据。
3. 继承(inheritance)：子类在“继承”后可以使用父类的方法。
4. 覆盖(override)：子类可以重新定义继承自父类的方法，这个过程叫做覆盖。

使用类的好处

程序变化的时候，只需要修改相关类的相关方法。

类和对象

对象是靠类的模型造出来的。对象包括实例变量(instance variable)，它们代表对象的状态；以及方法(methods)，它们是对象可以执行的动作。

比如，每个图形都有形状和颜色等特征，但是每个实例不尽相同，有各自的特征。

目前学习的参考书籍是《Head First Java》