原理：
- 将字符串转换成char字符数组
- 然后使用另一个数组存储
代码如下 public class CalChar {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String string = scanner.next(); char[] ch = new char[string.length()];
int[] nums = new int[26];
ch =string.toCharArray(); for (int i = 0; i < string.length(); i++) { nums[ch[i]-97]=ch[i]-97; //这里较为巧妙，将底层字母ascii码转换成数组下标
} }
}
加强版：统计数字，大写字母，小写字母
import java.util.Arrays;
import java.util.Scanner;
public class CalChar {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String string = scanner.next();
char[] ch = new char[string.length()];
int[] lowNum = new int[26];// 小写字母
int[] upNum = new int[26];// 大写字母
int[] nums = new int[10];// 数字
ch = string.toCharArray();
for (int i = 0; i < string.length(); i++) {
// 小写字母 a~z =97 ~(97+26)
if (0 <= (ch[i] - 97) && (ch[i] - 97) <= 26) {
lowNum[ch[i] - 97]++;
}
// 大写字母 A~Z =65 ~(65+26)
if (0 <= (ch[i] - 65) && (ch[i] - 65) <= 26) {
upNum[ch[i] - 65]++;
}
// 数字 0~9 = 48 ~ (48+26)
if (0 <= (ch[i] - 48) && (ch[i] - 48) <= 9) {
nums[ch[i] - 48]++;
}
}
CalChar calChar = new CalChar();
calChar.lowCount(lowNum);
System.out.println();
calChar.upCount(upNum);
System.out.println();
calChar.count(nums);
}
public void count(int[] nums) {
//数字计数
for (int i = 0; i < nums.length; i++) {
if (nums[i] != 0) {
System.out.print((char)(i+48)+":"+nums[i]+"个"+"\t");
}
}
}
//小写字母计数
public void lowCount(int[] lowNum) {
for (int i = 0; i < lowNum.length; i++) {
if (lowNum[i] != 0) {
System.out.print((char) (i+97) + ":" + lowNum[i] + "个"+"\t");
}
}
}
//大写字母计数
public void upCount(int[] ch) {
for (int i = 0; i < ch.length; i++) {
if (ch[i] != 0) {
System.out.print((char) (i+65) + ":" + ch[i] + "个"+"\t");
}
}
}
}