帮助开关盒

Question

这是我的程序，它会计算所有空格，所有字母a，e，s，t大写或小写，但编译时出错，它会给我一个我的变量未被初始化。

可能有人来看看，并告诉我

import java.util.Scanner; 

public class Count 
{ 
    public static void main (String[] args) 
    { 
     String phrase; // a string of characters 
     int countBlank; // the number of blanks (spaces) in the phrase 
     int length;  // the length of the phrase 
     char ch;   // an individual character in the string 
     int countA=0,countE=0,countS=0,countT=0; 

    Scanner scan = new Scanner(System.in); 
     // Print a program header 
     System.out.println(); 
     System.out.println ("Character Counter"); 
     System.out.println(); 

     // Read in a string and find its length 
     System.out.print ("Enter a sentence or phrase: "); 
     phrase = scan.nextLine(); 
     length = phrase.length(); 


     // Initialize counts 
     countBlank = 0; 

     // a for loop to go through the string character by character 

     for (int i = 0; i < phrase.length(); i++) 
     { 
    if(phrase.charAt(i) == ' ') countBlank++; 
     } 
    switch(ch) { 
    case 'a': 
    case 'A': countA++; 
    break; 

    case 'e': 
    case 'E': countE++; 
    break; 

    case 's': 
    case 'S': countS++; 
    break; 

    case 't': 
    case 'T': countT++; 
    break; 

    } 

     // Print the results 
     System.out.println(); 
     System.out.println ("Number of blank spaces: " + countBlank); 
     System.out.println ("Number of a: " + countA); 
     System.out.println ("Number of e: " + countE); 
     System.out.println ("Number of s: " + countS); 
     System.out.println ("Number of t: " + countT); 
     System.out.println(); 
    } 

} 

Answer 1

这里有两个问题：一是当前字符是永远不会分配给CH和第二开关语句是不是里面你的for循环。

Answer 2

你有“开关（CH）”，但你从来没有赋予它的价值。你用“char ch”来声明它但这还不够。

也许你想做的事：你的循环的

ch = phrase.charAt(i); 

内。

所以你的组合代码可以是这样的：

import java.util.Scanner; 

public class Count 
{ 
    public static void main (String[] args) 
    { 
     String phrase; // a string of characters 
     int countBlank; // the number of blanks (spaces) in the phrase 
     int length;  // the length of the phrase 
     char ch;   // an individual character in the string 
     int countA=0,countE=0,countS=0,countT=0; 

    Scanner scan = new Scanner(System.in); 
     // Print a program header 
     System.out.println(); 
     System.out.println ("Character Counter"); 
     System.out.println(); 

     // Read in a string and find its length 
     System.out.print ("Enter a sentence or phrase: "); 
     phrase = scan.nextLine(); 
     length = phrase.length(); 


     // Initialize counts 
     countBlank = 0; 

     // a for loop to go through the string character by character 

     for (int i = 0; i < phrase.length(); i++) 
     { 
      if(phrase.charAt(i) == ' ') countBlank++; 
      ch = phrase.charAt(i); 

       switch(ch) { 
        case 'a': 
        case 'A': countA++; 
        break; 

        case 'e': 
        case 'E': countE++; 
        break; 

        case 's': 
        case 'S': countS++; 
        break; 

        case 't': 
        case 'T': countT++; 
        break; 
       } 
     } 


     // Print the results 
     System.out.println(); 
     System.out.println ("Number of blank spaces: " + countBlank); 
     System.out.println ("Number of a: " + countA); 
     System.out.println ("Number of e: " + countE); 
     System.out.println ("Number of s: " + countS); 
     System.out.println ("Number of t: " + countT); 
     System.out.println(); 
    } 

} 

Answer 3

你写

switch(ch) 

但是变量ch从未赋值。

Answer 4

更改Ur for语句这样，开关必须包含在for中，并且ch应该被初始化为第i个字符。

for (int i = 0; i < phrase.length(); i++) 
       { 
       if(phrase.charAt(i) == ' ') 
        { 
         countBlank++; 
        } 
       ch = phrase.charAt(i); 

        switch(ch) 
        { 
         case 'a': 
         case 'A': countA++; 
         break; 

         case 'e': 
         case 'E': countE++; 
         break; 

         case 's': 
         case 'S': countS++; 
         break; 

         case 't': 
         case 'T': countT++; 
         break; 

        } 
       }