java - 在构建字符串并将它们添加到 ArrayList 时出错

Question

我正在做一个最终项目，这里是项目的信息和我得到的错误:
我们应该模拟一种名为“compAlien”的生命形式，看看它们如何相互 react 。这些外星人的创造方式是使用 128 个字符长且仅由字母 X、Y 或 Z 组成的遗传密码。
根据一些规则，我们应该计算并找到有关这些外星人的此类信息(例如，如果遗传密码中有 20 个 X，它的眼睛颜色将变为蓝色等)，创建一个包含此信息的字符串并它到一个ArrayList。我能够创建代码(如下所示)，但大多数时候当我尝试创建多个外星人时，我总是收到一条错误消息:

 Exception in thread "main" java.lang.StringIndexOutOfBoundsException:
 String index out of range: 128     at
 java.base/java.lang.StringLatin1.charAt(StringLatin1.java:48)  at
 java.base/java.lang.String.charAt(String.java:709)     at
 compAlien.calculateHealth(compAlien.java:75)   at
 compAlien.generateCompAlienInfos(compAlien.java:34)    at
 compAlien.main(compAlien.java:193)

这是我能够编写的代码:

import java.util.Scanner;
import java.util.ArrayList;

public class compAlien {
    
    static Scanner input = new Scanner(System.in);
    static ArrayList<String> compAlienInfos = new ArrayList<String>();
    static String geneticCode = "";
    static String compAlienInfo = "";
    static int colonySize = 0;
    static int count = 0;
    
    public static void generateGeneticCode() { //Method for creating the genetic codes of the compAliens.
            
        for(int i = 0; i < 128; i++) {
            
            char geneticCodeChar = (char) ('X' + Math.random() * ('Z' - 'X' + 1));
            geneticCode += geneticCodeChar;
            
        }
        
    }
    
    public static void generateCompAlienInfos() { //Method for creating all the info of the compAliens, assigning them an ID and adding their info to the compAlienInfos ArrayList.
        
        while(count < colonySize) {
            
            geneticCode = "";
            compAlienInfo = "";
            compAlienInfo += "ID:" + (count + 1) + ", ";
            
            generateGeneticCode();
            findGender();
            calculateHealth();
            findSkinTone();
            findEyeColor();
            
            compAlienInfos.add(compAlienInfo);
            System.out.println(compAlienInfo);
            count ++;
            
        }
        
    }
    
    public static void findGender() { //Method for finding the gender of the compAliens.
        
        if(geneticCode.charAt(127) == 'X') {
            
            compAlienInfo += "Gender: Female, ";
            
        }
        
        else if(geneticCode.charAt(127) == 'Y') {
            
            compAlienInfo += "Gender: Male, ";
            
        }
            
        else {
            
            compAlienInfo += "Gender: Female, ";
            
        }   
        
    }
    
    public static void calculateHealth() { //Method for calculating the health of the compAliens.
        
        int health = 1;
        int i = 0;
        
        while(i < 127) {
            
        if(geneticCode.charAt(i) == 'Y' && geneticCode.charAt(i + 1) == 'X' && geneticCode.charAt(i + 2) == 'Z') {
            
            health ++;
        
            }
        
        i++;
        
        }
        
        compAlienInfo += "Health: " + health + ", ";
        
    }
    
    public static void findEyeColor() { //Method for finding the eye color of the compAliens.
        
        int xCount = 0;
        
        for(int i = 0; i < 128; i++) {
            
            if(geneticCode.charAt(i) == 'X') {
                
                xCount ++;
                
            }
            
        }
        
        if(xCount <= 10) {
            
            compAlienInfo += "Eye Color: Green";
            
        }
        
        else if (10 < xCount && xCount <= 25) {
            
            compAlienInfo += "Eye Color: Blue";
            
        }
        
        else {
            
            compAlienInfo += "Eye Color: Brown";
            
        }
        
    }
    
    public static void findSkinTone() { //Method for finding the skin tone of the compAliens.
        
        int yCount = 0;
        
        for(int i = 0; i < 128; i++) {
            
            if(geneticCode.charAt(i) == 'Y') {
                
                yCount ++;
                
            }
            
        }
        
        if(20 <= yCount && yCount < 30) {
            
            compAlienInfo += "Skin Tone: Red ";
            
        }
        
        else if (30 <= yCount && yCount <= 40) {
            
            compAlienInfo += "Skin Tone: Green, ";
            
        }
        
        else {
            
            compAlienInfo += "Skin Tone: Orange, ";
            
        }
        
    }

    public static void main(String[] args) {
        
        System.out.println("Enter the population size of the compAlien colony: ");
        colonySize = input.nextInt();
        
        System.out.println("Simulating the compAlien colony...");
        generateCompAlienInfos();

    }
    
}

Answer 1

根据堆栈跟踪，在 calculateHealth()方法，此行试图访问字符串中不存在的位置的字符。更具体地说是 charAt() 调用，如下所示。该索引可能大于遗传代码字符串的长度。

if (geneticCode.charAt(i) == 'Y' && geneticCode.charAt(i + 1) == 'X' && geneticCode.charAt(i + 2) == 'Z')