package demo;
import java.util.Scanner;
public class Welcome {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.print("Enter a letter: ");
Scanner input = new Scanner(System.in);
String[] number={“2”,“3”,“4”,“5”,“6”,“7”,“8”,“9”};
char l = input.nextLine().charAt(0);
if(l==‘a’||l==‘b’||l==‘c’||l==‘A’||l==‘B’||l==‘C’)
System.out.printf(“The corresponding number is %s”, number[0]);
else if(l==‘d’||l==‘e’||l==‘f’||l==‘D’||l==‘E’||l==‘F’)
System.out.printf(“The corresponding number is %s”, number[1]);
else if(l==‘g’||l==‘h’||l==‘i’||l==‘G’||l==‘H’||l==‘I’)
System.out.printf(“The corresponding number is %s”, number[2]);
else if(l==‘j’||l==‘k’||l==‘l’||l==‘J’||l==‘K’||l==‘L’)
System.out.printf(“The corresponding number is %s”, number[3]);
else if(l==‘m’||l==‘n’||l==‘o’||l==‘m’||l==‘n’||l==‘o’)
System.out.printf(“The corresponding number is %s”, number[4]);
else if(l==‘p’||l==‘q’||l==‘r’||l==‘s’||l==‘P’||l==‘Q’||l==‘R’||l==‘S’)
System.out.printf(“The corresponding number is %s”, number[5]);
else if(l==‘t’||l==‘u’||l==‘v’||l==‘T’||l==‘U’||l==‘V’)
System.out.printf(“The corresponding number is %s”, number[6]);
else if(l==‘w’||l==‘x’||l==‘y’||l==‘z’||l==‘W’||l==‘X’||l==‘Y’||l==‘Z’)
System.out.printf(“The corresponding number is %s”, number[7]);
else
System.out.println(l+“is an invalid input”);;
}
}
[](()4.16
=================================================================
package demo;
import java.util.Scanner;
public class Welcome {
public static void main(String[] args) {
// TODO Auto-generated method stub
int l = (int)(Math.random()*26);
char letter=(char)(Math.random()*26+‘A’);
System.out.print("The random number is "+letter);
}
}
[](()4.17
=================================================================
package demo;
import java.util.Scanner;
public class Welcome {
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 i = new Scanner(System.in);
System.out.print("Enter a month: ");
String month = i.nextLine();
boolean isLeapYear = ((year % 4 == 0 && year % 100 != 0)||(year % 400 == 0));
switch(month){
case “Jan”:
case “Mar”:
case “May”:
case “Jul”:
case “Aug”:
case “Oct”:
case “Dec”:
System.out.println(month+" “+year+” has 31 day");
break;
case “Apr”:
case “Jun”:
case “Sep”:
case “Nov”:
System.out.println(month+" “+year+” has 30 days");
break;
case “Feb”:
if(isLeapYear){
System.out.println(month+" “+year+” has 29 days");
}else{
System.out.println(month+" “+year+” has 28 days");
}
default:
System.out.printf(“%s is not a correct month name”, month);
}
}
}
[](()4.18
=================================================================
package demo;
import java.util.Scanner;
public class Welcome {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.print("Enter two characters: ");
String s = input.nextLine();
char s1 = s.charAt(0);
char s2 = s.charAt(1);
switch(s1)
{
case ‘M’:
System.out.print("Mathematics ");
switch(s2){
case ‘1’:
System.out.println(“Freshman”);
break;
case ‘2’:
System.out.println(“Sophomore”);
break;
case ‘3’:
System.out.println(“Junior”);
break;
case ‘4’:
System.out.println(“Senior”);
break;
default:
;
}
break;
case ‘C’:
System.out.print("Computer science ");
switch(s2){
case ‘1’:
System.out.println(“Freshman”);
break;
case ‘2’:
System.out.println(“Sophomore”);
break;
case ‘3’:
System.out.println(“Junior”);
break;
case ‘4’:
System.out.println(“Senior”);
break;
default:
;
}
break;
case ‘I’:
System.out.print("information technology ");
switch(s2){
case ‘1’:
System.out.println(“Fre 《大厂前端面试题解析+Web核心总结学习笔记+企业项目实战源码+最新高清讲解视频》无偿开源 徽信搜索公众号【编程进阶路】 shman”);
break;
case ‘2’:
System.out.println(“Sophomore”);
break;
case ‘3’:
System.out.println(“Junior”);
break;
case ‘4’:
System.out.println(“Senior”);
break;
default:
;
}
break;
default:
System.out.print(“Invalid input”);
}
}
}
[](()4.19
=================================================================
package demo;
import java.util.Scanner;
public class Welcome {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.print("Enter the first 9 digits of an ISBN as String: ");
String a = input.next();
int sum=0;
for(int i=1;i<=9;i++)
sum+=(a.charAt(i-1)-‘0’)*i;
int tail = sum%11;
if(tail==10)
a=a+“X”;
else
a=a+tail;
System.out.println("The ISBN-10 number is "+a);
}
}
[](()4.20
=================================================================
package demo;
import java.util.Scanner;
public class Welcome {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.print("Enter a string: ");
String s1 = input.nextLine();
System.out.println(“长度为： " + s1.length()+” ; "+"第一个字符为： "+s1.charAt(0));
}
}
[](()4.21
=================================================================
package demo;
import java.util.Scanner;
public class Welcome {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.print("Enter a SSN: ");
Scanner input = new Scanner(System.in);
String a = input.next();
boolean valid = true;
if(a.length()!=11)
valid=false;
else
{
for(int i=0;i<=2;i++)
valid=valid&&(a.charAt(i)>=‘0’&&a.charAt(i)<=‘9’);
valid=valid&&(a.charAt(3)==‘-’);
for(int i=4;i<=5;i++)
valid=valid&&(a.charAt(i)>=‘0’&&a.charAt(i)<=‘9’);
valid=valid&&(a.charAt(6)==‘-’);
for(int i=7;i<=10;i++)
valid=valid&&(a.charAt(i)>=‘0’&&a.charAt(i)<=‘9’);
}
if(valid)
System.out.println(a+" is a valid SSN");
else
System.out.println(a+" is an invalid SSN");
}
}
[](()4.22
=================================================================
package demo;
import java.util.Scanner;
public class demo2 {
public static void main(String[] args) {
