第四章 数学函数、字符和字符串
4.2 常用数学函数
方法分三类：三角函数方法（trigonometric method）、指数函数方法（exponent method）和服务方法（service method）
4.4 String类型
String类型不是基本类型，而是引用类型（reference type）。
4.5.3 使用字符串修改彩票程序
package com.chapter4;
import java.util.Scanner;
public class LotteryUsingString {
/**
* 使用字符串修改彩票程序
*/
public static void main(String[] args) {
String lottery=""+(int)(Math.random()*10)+(int)(Math.random()*10);
Scanner input=new Scanner(System.in);
System.out.println("输入您的彩票号码(两位数): ");
String guess=input.nextLine();
char lotteryDigit1=lottery.charAt(0);
char lotteryDigit2=lottery.charAt(1);
char guessDigit1=guess.charAt(0);
char guessDigit2=guess.charAt(1);
System.out.println("中奖号码为: "+lottery);
if(guess.equals(lottery)){
System.out.println("恭喜您获得10000美元");
}else if(guessDigit1==lotteryDigit2 && guessDigit2==lotteryDigit1 ){
System.out.println("恭喜您获得3000美元");
}else if(guessDigit1==lotteryDigit1
|| guessDigit1==lotteryDigit2
|| guessDigit2==lotteryDigit1
|| guessDigit2==lotteryDigit2){
System.out.println("恭喜您获得1000美元");
}else{
System.out.println("不好意思，您没有中奖！");
}
}
}
4.6 格式化控制输出
package com.chapter4;
public class FormatDemo {
/**
* 使用printf来显示一个表格的程序
*/
public static void main(String[] args) {
System.out.printf("%-10s%-10s%-10s%-10s%-10s\n", "度(Degrees)", "弧度(Radians)", "正弦(Sine)", "余弦(Cosine)",
"正切(Tangent)");
int degrees = 30;// 度
double radians = Math.toRadians(degrees);
System.out.printf("%-10d%-10.4f%-10.4f%-10.4f%-10.4f\n", degrees, radians, Math.sin(radians), Math.cos(radians),
Math.tan(radians));
degrees = 60;
radians = Math.toRadians(degrees);
System.out.printf("%-10d%-10.4f%-10.4f%-10.4f%-10.4f\n", degrees, radians, Math.sin(radians), Math.cos(radians),
Math.tan(radians));
}
}