Java-基本概念

Java的工作方式

此例为交互式派对邀请系统。

Java的程序结构

Java的类

每个Java程序至少会有一个类以及一个main()。每个应用程序只能有一个main()函数。

语句、循环、条件分支

语句

声明、设定、调用方法等普通语句。

int x = 3;
String name= "zhangsan" ;
x = x * 7;
System.out.print("x = " + x);
double d = Math.random();
//注释行

循环

反复做某件事

while (x>12) {
    x = x - 1;
}for (int x = 0;x < 10;x++) {
    System.out.print("x = " + x);
}

条件分支

在适当的条件下做某件事

if(x == 0) {
    System.out.print("x 是 0");
} else {
    System.out.print("x 不是 0");
}

注

• 语句是以分号结束
• 程序块以{ }画出范围
• 以两条斜线开始的行是注释
• 空格符通常无关紧要
• 用名称与类型（type）来声明变量
• 类型与方法都必须定义在花括号{ }中
• 等号是赋值运算符
• 两个等号用来当等式等号运算符
• 只要条件测试结果为真，while循环就会一直执行块内的程序
• System.out.print与 System.out.println 差别在println 会再最后面插入换行

编写程序

专家术语学习机

public class PhraseOMatic {
    public static void main(String[] args) {
    // 专家术语String[] wordListOne = {
     "24/7", "multiTier", "30,000 foot", "B-to-B", "win-win", "frontend","web-based", "pervasive", "smart", "sixsigma", "critical-path", "dynamic" };String[] wordListTwo = {
     "empowered", "sticky", "value-added", "oriented", "centric", "distributed","clustered", "branded", "outside-the-box", "positioned", "networked", "focused","leveraged", "aligned", "targeted", "shared", "cooperative", "accelerated" };String[] wordListThree = {
     "process", "tippingpoint", "solution", "architecture", "core competency","strategy", "mindshare", "portal", "space", "vision", "paradigm", "mission" };// 计算每组有多少名词术语int oneLength = wordListOne.length;int twoLength = wordListTwo.length;int threeLength = wordListThree.length;// 产生随机数int rand1 = (int) (Math.random() * oneLength);int rand2 = (int) (Math.random() * twoLength);int rand3 = (int) (Math.random() * threeLength);// 组合出专家术语String phrase = wordListOne[rand1] + " " + wordListTwo[rand2] + " " + wordListThree[rand3];// 输出System.out.println("What we need is a " + phrase);}
}