计算字符串中字母的出现次数

我试图在Java中编写一个for循环来计算字符串中字母的出现次数。 用户将输入要计数的字母和要搜索的字符串。 这是一个非常基本的代码，我们尚未获得数组或其他许多代码。 （我意识到我曾两次宣布信件，但此时我的大脑已经死了）这是我到目前为止所尝试的并且遇到麻烦，任何帮助都表示赞赏：

好的，我根据建议更改了我的代码，但现在它只是读了我的句子的第一个单词？

import java.util.Scanner; public class CountCharacters { public static void main(String[] args) { Scanner in = new Scanner(System.in); char letter; String sentence = ""; System.out.println("Enter a character for which to search"); letter = in.next().charAt(0); System.out.println("Enter the string to search"); sentence = in.next(); int count = 0; for (int i = 0; i < sentence.length(); i++) { char ch = sentence.charAt(i); if (ch == letter) { count++; } } System.out.printf("There are %d occurrences of %s in %s", count, letter, sentence); } } 

Answer 1

我看到了几个问题。 首先，您有两个具有相同名称的变量。

第二个你的if条件检查句子的长度大于0而不是检查字符相等。

 Scanner in = new Scanner(System.in); char inLetter = ""; String sentence = ""; System.out.println("Enter a character for which to search"); inLetter = in.next().charAt(0); System.out.println("Enter the string to search"); sentence = in.next(); int letter = 0; for (int i = 0; i < sentence.length(); i++) { char ch = sentence.charAt(i); if (inLetter == ch) { letter++; } } System.out.print(sentence.charAt(letter)); 

我还强烈建议validation输入（在上面的例子中没有完成），而不是假设你从第一个输入中得到1个字符，在第二个输入中得到1个字符。

Answer 2

你的if (sentence.length() <= 0) {不对。 改变你的状况，如：

 System.out.println("Enter a character for which to search"); letter = in.next(); System.out.println("Enter the string to search"); sentence = in.next(); char searchLet=letter.charAt(0); // Convert String to char int letter = 0; for (int i = 0; i < sentence.length(); i++) { char ch = sentence.charAt(i); if (searchLet== ch) { // Check the occurrence of desired letter. letter++; } } System.out.print(sentence.charAt(letter)); 

Answer 3

 if (sentence.length() <= 0) { letter++; } 

程序中的上述代码部分是错误的。 除非您输入空字符串，否则这将永远不会成立。

基本上这不是正确的逻辑。 您将不得不使用直接比较。

Answer 4

无需循环：

  String sentence = "abcabcabcd"; String letter = "b"; int numOfOccurences = sentence.length() - sentence.replaceAll(letter, "").length(); System.out.println("numOfOccurences = "+numOfOccurences); 

OUTPUT：

 numOfOccurences = 3 

Answer 5

试试这个

forget String letter = "" < - 删除
忘记letter = in.next() < - 删除

  // There's no nextChar() method, so this is a work aroung char ch = in.findWithinHorizon(".", 0).charAt(0); int letter = 0; for (int i = 0; i < sentence.length(); i++) { if (sentence.charAt(i) == ch) { letter++; } } System.out.println(letter); // print number of times letter appears // You don't want this System.out.print(sentence.charAt(letter)); // Makes no sense 

Answer 6

尝试这个：

 Char letter = ''; String sentence = ""; System.out.println("Enter a character for which to search"); letter = in.next().charAt(0); System.out.println("Enter the string to search"); sentence = in.next(); int count= 0; for (int i = 0; i < sentence.length(); i++) { char ch = sentence.charAt(i); if (ch==letter) { count++; } } System.out.print(letter+" occurance:"+count); 

Answer 7

1. 你需要知道你想搜索的字符。 你可以使用char charToSearch = letter.toCharArray（）[0];
2. 定义一个变量，例如count，以计算给定字符串中字母的出现次数。
3. 循环字符串并比较每个char，如果char等于要搜索的char，则count ++;

实施例—>

 int count = 0; char charToSearch = letter.toCharArray()[0]; for (int i = 0; i < sentence.length(); i++) { if (sentence.charAt(i) == charToSearch) { count++; } } System.out.printf("Occurrences of a %s in %s is %d", letter, sentence, count); 

Answer 8

希望这对你有所帮助。

 import java.util.Scanner; public class CountCharacters { public static void main(String[] args) { Scanner in = new Scanner(System.in); System.out.println("Enter the string to search"); String sentence = in.nextLine(); System.out.println("Enter a character for which to search"); String letter = in.next(); int noOfOccurance = 0; for (int i = 0; i < sentence.length(); i++) { char dh=letter.charAt(0); char ch = sentence.charAt(i); if (dh==ch) { noOfOccurance++; } } System.out.print(noOfOccurance); } } 

输入输出样本 ：

 Enter the string to search how are you Enter a character for which to search o No of Occurances : 2 

Answer 9

尝试indexOf（）方法。 它应该工作

Answer 10

读取字符后，您的Scanner类没有移动到下一行

 letter = in.next().charAt(0); 

在读取输入字符串之前添加另一个in.nextLine（）

  System.out.println("Enter a character for which to search"); letter = in.next().charAt(0); in.nextLine(); System.out.println("Enter the string to search"); sentence = in.nextLine(); 

老线程，但希望这有助于:)