Java区分大小写字母数字和符号

Posted 2020-06-17

java如何区分如题的四种东西呢？首先我想到的是利用ASCII码，因为不同的符号的ASCII码是不一样的。而要利用ASCII码区分的话，至少要知道A，Z，a，z，0，9的ASCII码，这样就可以利用ASCII码来区分了。

这是第一种方法。

 1 package test;
 2 import java.util.Scanner;
 3 public class Differentiate{
 4     public static void main(String[] args){
 5         // A-65,Z-90,a-97,z-122,0-48,9-57
 6         Scanner sc = new Scanner(System.in);
 7         String nextLine = sc.nextLine();
 8         char[] charArray = nextLine.toCharArray();
 9         for(int i = 0;i<charArray.length;i++){
10             int charAscii = (int)charArray[i];
11             if(charAscii >=65 && charAscii <=90){
12                 System.out.print("大写字母:");
13                 System.out.println(charArray[i]);
14             }else if(charAscii >=97 && charAscii <=122){
15                 System.out.print("小写字母:");
16                 System.out.println(charArray[i]);
17             }else if(charAscii >= 48 && charAscii <= 57){
18                 System.out.print("数字:");
19                 System.out.println(charArray[i]);
20             }else{
21                 System.out.print("符号:");
22                 System.out.println(charArray[i]);
23             }
24         }
25     }
26 }

第二种方法，在网上查资料查到的，貌似在java里面对A-Z，a-z,0-9的char字符都有排序的，所以可以直接比较。

 1 package test;
 2 
 3 import java.util.Scanner;
 4 
 5 public class Differentiate{
 6     public static void main(String[] args) {
 7         Scanner sc = new Scanner(System.in);
 8         String nextLine = sc.nextLine();
 9         for (int i = 0; i < nextLine.length(); i++) {
10             char c = nextLine.charAt(i);
11             if (c >= ‘A‘ && c <= ‘Z‘) {
12                 System.out.print("max ");
13                 System.out.println(c);
14             } else if (c >= ‘a‘ && c <= ‘z‘) {
15                 System.out.print("min ");
16                 System.out.println(c);
17             } else if (c >= ‘0‘ && c <= ‘9‘) {
18                 System.out.print("数字 ");
19                 System.out.println(c);
20             } else {
21                 System.out.print("符号");
22                 System.out.println(c);
23             }
24         }
25     }
26 }

还有一种方法，利用indexOf()函数，如果某个字符在字符串里面不存在，就会返回-1，所以只需要先做出A-Z,a-z,0-9三个字符串，然后每次用这三个字符串判断就行了

 1 package test;
 2 
 3 import java.util.Scanner;
 4 
 5 public class Differentiate{

 6     public static void main(String[] args) {
 7         Scanner sc = new Scanner(System.in);
 8         String nextLine = sc.nextLine();
 9         String upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
10         String lower = "abcdefghijklmnopqrstuvwxyz";
11         String num = "0123456789";
12         char[] charArray = nextLine.toCharArray();
13         for(int i = 0;i<charArray.length;i++){
14             if(upper.indexOf(charArray[i]) != -1){
15                 System.out.print("大写字母:");
16                 System.out.println(charArray[i]);
17             }else if(lower.indexOf(charArray[i]) != -1){
18                 System.out.print("小写字母:");
19                 System.out.println(charArray[i]);
20             }else if(num.indexOf(charArray[i]) != -1){
21                 System.out.print("数字:");
22                 System.out.println(charArray[i]);
23             }else{
24                 System.out.print("符号:");
25                 System.out.println(charArray[i]);
26             }
27         }
28     }
29 }