Java Programming: Enter a string of lowercase strings to count the occurrences of each letter

* Requirement: Count each letter in the string:
* Description: Write a program prompting the user to enter a string,
* Then count the number of occurrences of each letter in the string, ignoring the case of the letter.
*
Principle
* 1. Use the toLowerCase () method in the string class to convert uppercase letters in strings to lowercase.
* 2. Constructs an array with 26 int worth of CH, and each element records the number of occurrences of a letter.
* i.e., ch[0] records the number of a, ch[1] the number of records B.
* 3. For each character in the character, determine if it is a lowercase letter, and if so, the corresponding counter in the array is incremented by 1.

The first style of source code:

Package fourth day; Import Java.util.scanner;public class statistic character {public static void main (string[] args) {Scanner sc = new Scanner (S ystem.in); int[] A = new int[26];//array holds the number of occurrences of the corresponding 26 letters, such as a[0], the number of occurrences of the letter A, the value of a[2] corresponds to the number of occurrences of c ... System.out.println ("Please enter a string of lowercase strings"); String str=sc.nextline (); Str=str.trim (). toLowerCase ();//Remove front and back spaces and turn all lowercase letters//This for loop to find the number of occurrences of each letter for (int i = 0; i < Str.length (); i++) {char c = str.charat (i);//Take out each letter int index=c-' a ';//This allows you to get an array of each letter corresponding to the subscript a[index]=a[index]+1;//corresponding letters appear the array of letters and 1}/ /This for loop prints the number of occurrences of each letter and does not print output for (int i = 0; i < a.length; i++) {if (a[i]!=0)//equals 0 The letter does not appear and there is no need to print {SYSTEM.OUT.PRINTLN ("Letter" + (char) (i+ ' a ') + "appears:" +a[i]+ ");}}}

the first style of source code:To wrap the number of statistical letters into a static method

Package  The third day _ exercises; Import Java.util.scanner;public class statistics number of characters {//static method counts the number of occurrences of each letter public static int[] Countletters ( String str) {int[] a = new int[26];//this for loop to find the number of occurrences of each letter for (int i = 0; i < str.length (); i++) {char c = str.charat (i);// Take out each letter int index = c-' a ';//So you can get the array subscript for each letter A[index] = A[index] + 1;//The corresponding letter appears, the array of letters is stored plus 1}return A;} public static void Main (string[] args) {Scanner sc = new Scanner (system.in); String str = sc.nextline (); int[] A = countletters (str);//Call the function that counts the occurrences of each letter, the return type is an array//this for loop prints the number of occurrences of each letter, and does not print output for (int i = 0; i < a.length; i++) {if (a[i]!=0)//equals 0 equivalent to this letter does not appear there is no need to print {System.out.println ("letter" + (char) (i+ ' a ') + "appears:" +a[i]+ "Times");}}}

Java Programming: Enter a string of lowercase strings to count the occurrences of each letter