Java语言程序设计基础篇原书第十版第四章编程练习题答案
决定和java死磕到底了，这是要。最近有几个入门级别的童鞋加我好友取经，其实这本书真的还可以的。可以慢慢的学习，不急于求成，慢慢来懂的就会越来越多的。我会继续把自己做的东西拿出来分享，希望对大家有所帮助吧。
4.1几何：五边形的面积
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter the lenght from the center to a vertex:");
double r=input.nextDouble();
double s=2*r*Math.sin(Math.PI/5);
double area=(5*Math.pow(s, 2))/(4*Math.tan(Math.PI/5));
System.out.printf("The area of the pentagon is%4.2f ",area);
}
}
4.2几何：最大圆距离
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter point 1(latitude and longitude) in degress ");
String s1=input.nextLine();
System.out.print("Enter point 2(latitude and longitude) in degress ");
String s2=input.nextLine();
double x1=Double.parseDouble(s1.split(",")[0]);
//因为运行实例是用逗号隔开，所以这里也用逗号吧，这个split课本中可能漏讲了，自己补充吧
double y1=Double.parseDouble(s1.split(",")[1]);
double x2=Double.parseDouble(s2.split(",")[0]);
double y2=Double.parseDouble(s2.split(",")[1]);
final double r=6371.01;
double result=r*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));
System.out.println("The distance between the two points is "+result+"km");
}
}
4.3几何：估算面积
这题。。。
这道题。。。
这道题吧。。。
自己做好不~懒得去百度这么多东西啦！
4.4几何：六边形面积
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter the side:");
double s=input.nextDouble();
double area=(6*Math.pow(s, 2))/(4*Math.tan(Math.PI/6));
System.out.printf("The area of the pentagon is%4.2f ",area);
}
} 4.6圆上的随机点
这道题我没有看懂他的要求，有理解能力好点的可以在评论里告诉我。十分感谢4.7顶点坐标
做这道题目前先了解下三角函数吧，巩固下高中知识做起来就容易很多了。我也是看了很久的。
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter the radius of the bounding circle:");
double radius=input.nextDouble();
double p2x=0;
double p2y=100;
double p3x=Math.cos(Math.PI/10)*(-1)*radius;
double p3y=Math.sin(Math.PI/10)*radius;
double p1y=Math.sin(Math.PI/10)*radius;
double p1x=Math.cos(Math.PI/10)*radius;
double p4y=Math.sin((3*Math.PI)/10)*(-1)*radius;
double p4x=Math.cos((3*Math.PI)/10)*(-1)*radius;
double p5y=p4y;
double p5x=Math.cos((3*Math.PI)/10)*radius;
System.out.println("P1:"+"("+p1x+","+p1y+")");
System.out.println("P2:"+"("+p2x+","+p2y+")");
System.out.println("P3:"+"("+p3x+","+p3y+")");
System.out.println("P4:"+"("+p4x+","+p4y+")");
System.out.println("P5:"+"("+p5x+","+p5y+")");
}
} 4.8给出ASCII码对应的字符
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter an ASCII code:");
int number=input.nextInt();
if(number>=1&&number<=127){
char ch=(char)number;
System.out.println("The character for ASCII code is :"+ch);
}
else
System.exit(1);
}
} 4.9给出字符的Unicode码
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a character :");
String character=input.nextLine();
if(character.length()!=1){
System.out.println("You must enter exactly one character!!!");
System.exit(1);
}
char ch=character.charAt(0);
if((ch>='A'&&ch<='Z')||(ch>='a'&&ch<='z')){
int interger=(int)ch;
System.out.println("The Unicode for the character"+ch+" is"+interger);
}else
System.exit(1);
}
} 4.11十进制转十六进制
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a decimal value(0 to 15) :");
int number=input.nextInt();
if(number>=0&&number<=9){
System.out.println("The hex value is "+number);
}
else if(number>=10&&number<=15){
char ch=(char)(number+'A'-10);
System.out.println("The hex value is "+ch);
}
else
System.out.println(number+" is an invalid input");
}
} 4.12十六进制转二进制
本人习惯偷懒，这道题虽然没有星星，但是也是让我头痛了很久，最终在API中找到了这两个函数，完美的额解决了这个题，真的很兴奋。API无敌！如果要和书本一致的话，自己增加个循环吧，当输入的不是16进制的时候直接System.exit（1）。
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a hex digit :");
String number=input.nextLine();
int inter = Integer.parseInt(number, 16);//这个函数是把16进制转化为十进制，把这个值给inter
String str = Integer.toBinaryString(inter);//把inter这个十进制的值直接转为二进制
System.out.println(str);
}
} 4.13判断元音还是辅音
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a letter:");
String str=input.nextLine();
char ch=str.charAt(0);
if(ch=='A'||ch=='a'){
System.out.println(ch+" is a vowel");
}
else if(ch=='E'||ch=='e'){
System.out.println(ch+" is a vowel");
}
else if(ch=='I'||ch=='i'){
System.out.println(ch+" is a vowel");
}
else if(ch=='O'||ch=='o'){
System.out.println(ch+" is a vowel");
}
else if(ch=='U'||ch=='u'){
System.out.println(ch+" is a vowel");
}
else
System.out.println(ch+" is a consonant");
}
} 4.14转换为字母等级的数字
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a letter grade(A、B、C、D、F) :");
String str=input.next();
char ch=str.charAt(0);
if (ch=='A'){
System.out.println("The numeric value for grade "+ch+"is 4");
}
else if(ch=='B'){
System.out.println("The numeric value for grade "+ch+"is 3");
}
else if(ch=='C'){
System.out.println("The numeric value for grade "+ch+"is 2");
}
else if(ch=='D'){
System.out.println("The numeric value for grade "+ch+"is 1");
}
else if(ch=='F'){
System.out.println("The numeric value for grade "+ch+"is 0");
}
else
System.out.println(ch+" is an invalid grade");
}
} 4.16随机字母
package nameyu;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
int number=(int)(65+Math.random()*26);
char ch=(char)number;
System.out.println(ch);
}
} 4.17一个月中的日期
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a year:");
int year=input.nextInt();
Scanner iput=new Scanner(System.in);
System.out.print("Enter a month:");
String month=iput.nextLine();
char ch1=month.charAt(0);
char ch2=month.charAt(1);
char ch3=month.charAt(2);
if(ch1=='J'&&ch2=='a'&&ch3=='n'){
System.out.println("Jan "+year+" has 31 days");
}
else if(ch1=='F'&&ch2=='e'&&ch3=='b'){
if((year%4==0&&year%100!=0)||(year%400==0)){
System.out.println("Feb "+year+" has 29 days");
}else
System.out.println("Feb "+year+" has 28 days");
}
else if(ch1=='M'&&ch2=='a'&&ch3=='r'){
System.out.println("Mar "+year+" has 31 days");
}
else if(ch1=='A'&&ch2=='p'&&ch3=='r'){
System.out.println("Apr "+year+" has 30 days");
}
else if(ch1=='M'&&ch2=='a'&&ch3=='y'){
System.out.println("May "+year+" has 31 days");
}
else if(ch1=='J'&&ch2=='u'&&ch3=='n'){
System.out.println("Jun "+year+" has 30 days");
}
else if(ch1=='J'&&ch2=='u'&&ch3=='l'){
System.out.println("Jul "+year+" has 31 days");
}
else if(ch1=='A'&&ch2=='u'&&ch3=='g'){
System.out.println("Aug "+year+" has 31 days");
}
else if(ch1=='S'&&ch2=='e'&&ch3=='p'){
System.out.println("Sep "+year+" has 30 days");
}
else if(ch1=='O'&&ch2=='c'&&ch3=='t'){
System.out.println("Oct "+year+" has 31 days");
}
else if(ch1=='N'&&ch2=='o'&&ch3=='v'){
System.out.println("Nov "+year+" has 30 days");
}
else if(ch1=='D'&&ch2=='e'&&ch3=='c'){
System.out.println("Dec "+year+" has 31 days");
}
}
} 4.18学生的专业和状况
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter two characters:");
String message=input.nextLine();
char str1=message.charAt(0);
char str2=message.charAt(1);
String major="";
String grade="";
if((str1=='M'||str1=='C'||str1=='I')&&(str2=='1'||str2=='2'||str2=='3'||str2=='4')){
if(str1=='M'){
major="Mathmatics";
}else if(str1=='C'){
major="Computer";
}else if(str1=='I'){
major="Infomation technology";
}
if(str2=='1'){
grade="Freshman";
}else if(str2=='2'){
grade="Sophomore";
}else if(str2=='3'){
grade="Junior";
}else if(str2=='4'){
grade="Senior";
}
System.out.println(major+" "+grade);
}else
System.out.println("Invalid input");
}
} 4.19商业：检测ISBN-10
字符零的十进制是48。
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a string of nine consecutive digits:");
String numbers=input.nextLine();
int d1=numbers.charAt(0)-48;
int d2=numbers.charAt(1)-48;
int d3=numbers.charAt(2)-48;
int d4=numbers.charAt(3)-48;
int d5=numbers.charAt(4)-48;
int d6=numbers.charAt(5)-48;
int d7=numbers.charAt(6)-48;
int d8=numbers.charAt(7)-48;
int d9=numbers.charAt(8)-48;
int d10=(d1+d2*2+d3*3+d4*4+d5*5+d6*6+d7*7+d8*8+d9*9)%11;
if (d10==10){
System.out.println(d1 + "" + d2 + "" + d3 + "" + d4 + "" + d5 + "" + d6 + "" + d7 + "" + d8 + "" + d9 + "" + "X");}
else
System.out.println(d1 + "" + d2 + "" + d3 + "" + d4 + "" + d5 +"" + d6 + "" + d7 + "" + d8 + "" + d9 + "" + d10);
}
}
4.20字符串处理
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a string:");
String numbers=input.nextLine();
int l=numbers.length();
char ch=numbers.charAt(0);
System.out.println("length :"+l);
System.out.println("first character :"+ch);
}
}4.21检查SSN
这题做的方法比较死板，有好的方法可以私信我。因为我觉得这个真的太低能了。属于暴力破解题目类型，有时候也还可以，但是数据多了就不合适了的。
！！！！！！！！！！！！！！
我知道了！！！这道题使用字符串和数字间的转换就可以了。
int intvalue=Interger.parseInter(intString);
intString是一个数值型字符串。如果不是字符型字符串就会报错。哇爆炸，我不想改了。你们修改下吧，思路已经说了呢。不懂评论里见~
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter a SSN:");
String ssn=input.nextLine();
if(ssn.length()==11){
if(ssn.charAt(3)=='-'&&ssn.charAt(6)=='-'){
String str1=ssn.substring(0,3);
String str2=ssn.substring(4,6);
String str3=ssn.substring(7);
if(str1.charAt(0)>='0'&&str1.charAt(0)<='9'){
if(str1.charAt(1)>='0'&&str1.charAt(1)<='9'){
if(str1.charAt(2)>='0'&&str1.charAt(2)<='9'){
if(str2.charAt(0)>='0'&&str2.charAt(0)<='9'){
if(str2.charAt(1)>='0'&&str2.charAt(1)<='9'){
if(str3.charAt(0)>='0'&&str3.charAt(0)<='9'){
if(str3.charAt(1)>='0'&&str3.charAt(1)<='9'){
if(str3.charAt(2)>='0'&&str3.charAt(2)<='9'){
if(str3.charAt(3)>='0'&&str3.charAt(3)<='9'){
System.out.println(ssn+" is a valid social security number");
}
}
}
}
}
}
}
}
}
}
}else
System.out.println(ssn+" is an invalid social security number");
}
}
4.22检测子串
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter string s1:");
String str1=input.next();
System.out.print("Enter string s2:");
String str2=input.next();
if(str1.indexOf(str2)>=0){
System.out.println(str2+" is a substring of "+str1);
}
else
System.out.println(str2+" is ont a substring of "+str1);
}
}
4.24对三个城市排序
package nameyu;
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
System.out.print("Enter the first city");
String city1=input.nextLine();
System.out.print("Enter the second city");
String city2=input.nextLine();
System.out.print("Enter the third city");
String city3=input.nextLine();
if(city1.compareToIgnoreCase(city2)<0){
if(city2.compareToIgnoreCase(city3)<0){
System.out.println("123"+city1+" "+city2+" "+city3);
}else if(city1.compareToIgnoreCase(city3)>0){
System.out.println("312"+city3+" "+city1+" "+city2);
}
if(city3.compareToIgnoreCase(city2)<0){
if(city2.compareToIgnoreCase(city1)<0){
System.out.println("321"+city3+" "+city2+" "+city1);
}else if(city3.compareToIgnoreCase(city1)>0){
System.out.println("132"+city1+" "+city3+" "+city2);
}
else if(city3.compareToIgnoreCase(city2)>0){
if(city3.compareToIgnoreCase(city1)<0){
System.out.println("231"+city2+" "+city3+" "+city1);
}
}
if(city1.compareToIgnoreCase(city3)<0){
if(city1.compareToIgnoreCase(city2)>0)
System.out.println("213"+city2+" "+city1+" "+city3);
}
}
}
}
}
4.25生成车牌号码
package nameyu;
public class Test {
public static void main(String[] args) {
// TODO Auto-generated method stub
char ch1=(char) (65+Math.random()*26);
char ch2=(char) (65+Math.random()*26);
char ch3=(char) (65+Math.random()*26);
String str1=String.valueOf(ch1);
String str2=String.valueOf(ch2);
String str3=String.valueOf(ch3);//把字符转换为字符串
int number1=(int) (Math.random()*10);
int number2=(int) (Math.random()*10);
int number3=(int) (Math.random()*10);
int number4=(int) (Math.random()*10);
// String str=str1+str2+str3;
System.out.println(str1+str2+str3+" "+number1+number2+number3+number4);
}
}4.26财务应用：货币单位
package nameyu;
import java.util.Scanner;
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input=new Scanner(System.in);
String str=input.nextLine();
if(str.indexOf('.')==-1){
System.out.println(str+" dollars"+" no cent");
}else if(str.indexOf('.')!=-1){
String dollars=str.substring(0,str.indexOf('.'));
String cent=str.substring(str.indexOf('.')+1);
System.out.println(dollars+" dollars "+cent+" cents");
}
}
}
这一章的题目，差不多都在这里了。如有问题可私信或者评论指出，欢迎大家指正。谢谢大家。