Java语言程序设计(基础篇) 第四章 数学函数、字符和字符串
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
1 package com.chapter4; 2 3 import java.util.Scanner; 4 5 public class LotteryUsingString { 6 /** 7 * 使用字符串修改彩票程序 8 */ 9 10 public static void main(String[] args) { 11 12 String lottery=""+(int)(Math.random()*10)+(int)(Math.random()*10); 13 14 Scanner input=new Scanner(System.in); 15 System.out.println("输入您的彩票号码(两位数): "); 16 String guess=input.nextLine(); 17 18 char lotteryDigit1=lottery.charAt(0); 19 char lotteryDigit2=lottery.charAt(1); 20 21 char guessDigit1=guess.charAt(0); 22 char guessDigit2=guess.charAt(1); 23 24 System.out.println("中奖号码为: "+lottery); 25 26 if(guess.equals(lottery)){ 27 System.out.println("恭喜您获得10000美元"); 28 }else if(guessDigit1==lotteryDigit2 && guessDigit2==lotteryDigit1 ){ 29 System.out.println("恭喜您获得3000美元"); 30 }else if(guessDigit1==lotteryDigit1 31 || guessDigit1==lotteryDigit2 32 || guessDigit2==lotteryDigit1 33 || guessDigit2==lotteryDigit2){ 34 System.out.println("恭喜您获得1000美元"); 35 }else{ 36 System.out.println("不好意思,您没有中奖!"); 37 } 38 } 39 40 }
4.6 格式化控制输出
1 package com.chapter4; 2 3 public class FormatDemo { 4 /** 5 * 使用printf来显示一个表格的程序 6 */ 7 8 public static void main(String[] args) { 9 10 System.out.printf("%-10s%-10s%-10s%-10s%-10s\n", "度(Degrees)", "弧度(Radians)", "正弦(Sine)", "余弦(Cosine)", 11 "正切(Tangent)"); 12 13 int degrees = 30;// 度 14 double radians = Math.toRadians(degrees); 15 System.out.printf("%-10d%-10.4f%-10.4f%-10.4f%-10.4f\n", degrees, radians, Math.sin(radians), Math.cos(radians), 16 Math.tan(radians)); 17 18 degrees = 60; 19 radians = Math.toRadians(degrees); 20 System.out.printf("%-10d%-10.4f%-10.4f%-10.4f%-10.4f\n", degrees, radians, Math.sin(radians), Math.cos(radians), 21 Math.tan(radians)); 22 } 23 24 }