循环和字段的 indexoutofboundsexception

Question

public class Task { 

    public static void main(String[] args) {
        String text ="a subject is the noun that is doing the main verb."; 
        int[] field = new int[26];
        int xy = 0; //xy will be the total number of the letter in the sentence


        char cd = 'a';
        for (int ef = 0; ef<= 25; ef++){
            for (int ab = 1; ab<= text.length(); ab++){
                    if (cd == text.charAt(ab)){ // Eclipse says that this line has problem (at CopyOfAufgabe_2.main(CopyOfAufgabe_2.java:13)
                        field[ef]=field[ef]+1;
                        xy++;
                    }
                }
            cd++;
            }
    }
}

``这个任务有两个目的：

1. find the total number of letters in the sentence
2. find the number of respective letter (i.e. how many "a"s, how many "b"s, etc. The numbers are assigned to the field created in the fifth line (one number for each object)) (It is assumed that every letter in the sentence is not capitalized.)

错误信息显示：

线程“主”java.lang.StringIndexOutOfBoundsException 中的异常：字符串索引超出范围：42 在 java.lang.String.charAt（未知来源） 在 CopyOfAufgabe_2.main(CopyOfAufgabe_2.java:13)``

Answer 1

for (int ef = 0; ef<= 25; ef++){

应该是

for (int ef = 0; ef< 25; ef++){

一个包含 25 个元素的数组的索引从 0 到 24。

for (int ab = 1; ab<= text.length(); ab++){

应该是

for (int ab = 0; ab< text.length(); ab++){

具有length() 字符的字符串的字符具有从0 到length()-1 的索引。