java - 向字符串添加字符

Question

import java.util.Random;

public class PasswordRandomizer {
    // Define the variables
    private Random random = new Random();
    private int passwordLength;
    private String password = "";

    public PasswordRandomizer(int length) {
        // Initialize the variable
        this.passwordLength = length;
    }

    public String createPassword() {
        // write code that returns a randomized password
        for(int i = 0; i < this.passwordLength; i++){
            int j = random.nextInt();
            char symbol = "abcdefghijklmnopqrstuvwxyz".charAt(j);
            this.password = this.password + symbol; 
        }
        return this.password;
    }
}

如何将字符添加到字符串中，我尝试了此操作，但收到此错误:

"Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -414383904".

Answer 1

因为random.nextInt()返回 -2,147,483,648 和 2,147,483,647 之间的值。

你想要的是random.nextInt("abcdefghijklmnopqrstuvwxyz".length())

我还会将“abcdefghijklmnopqrstuvwxyz”分配给一个常量。

private final static String ALPHABET = "abcdefghijklmnopqrstuvwxyz";

Char randomChar = ALPHABET.charAt(random.nextInt(ALPHABET.length()));