计算字符串中字母的出现次数 [英] Count the occurrences of a letter in a string

问题描述

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，我们还没有得到数组或其他许多东西。 （我意识到我宣布了两封信，但是我的大脑在这一点上已经死了）这是我迄今为止所尝试过的，遇到了麻烦，任何帮助表示赞赏：

好吧我改变了我的代码每个建议，但现在它只是读取我的句子的第一个字？

  import java。 util.Scanner; 
 
 public class CountCharacters {
 public static void main（String [] args）{
 Scanner in = new Scanner（System.in）; 
 
 char char; 
 String sentence =; 
 System.out.println（输入要搜索的字符）; 
 letter = in.next（）。charAt（0）; 
 System.out.println（输入要搜索的字符串）; 
 sentence = in.next（）; 
 
 int count = 0; 
 for（int i = 0; i< sentence.length（）; i ++）{
 char ch = sentence.charAt（i）; 
 if（ch == letter）{
 count ++; 
 $ b $ System.out.printf（％s％s中有％d次发生，count，
 letter，sentence）; 
 
 
 $ b $ / code $ / $ p 
 
解决方案
我看到一些问题。首先你有两个同名的变量。
 
 
 
其次，如果条件检查句子的长度大于0而不是检查字符是否相等。
 扫描仪输入= new Scanner（System.in）; 
 
 char inLetter =; 
 String sentence =; 
 System.out.println（输入要搜索的字符）; 
 inLetter = in.next（）。charAt（0）; 
 System.out.println（输入要搜索的字符串）; 
 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））; 
  
我也强烈建议验证输入（不是在上面的例子中）假设你从第一个输入中获得1个字符，在第二个中获得1个句子。
 
I am trying to write a for loop in Java that will count the occurrences of a letter in a string. The user will enter the letter to count and the string in which to search. This is a very basic code, and we have not gotten to arrays or much else yet. (I realize that I declared letter twice, but my brain is dead at this point) This is what I have tried so far and am having trouble with, any help is appreciated: 

Ok I changed my code per suggestions, but now it is only reading the first word of my sentence?
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);

}
}

解决方案
I see a couple of issues.  First you have two variables with the same name.

Second your if condition check for the lenght of the sentence to be greater then 0 instead of checking for character equality.
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));
I would also strongly suggest to validate the input (which is not done in the example above) instead of just assuming you got 1 character from the first input and 1 sentence in the second.

                        
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