小编Uko*_*koM的帖子

import java.util.ArrayList;
import java.util.Collections;

public class SmartCombining {
    public static void main(String[] args) {
        ArrayList<Integer> list1 = new ArrayList<Integer>();
        ArrayList<Integer> list2 = new ArrayList<Integer>();

        Collections.addAll(list1, 4, 3);
        Collections.addAll(list2, 5, 10, 4, 3, 7);

        smartCombine(list1, list2);
        System.out.println(list1);
        System.out.println(list2);
    }

    public static void smartCombine(ArrayList<Integer> first,
            ArrayList<Integer> second) {
        first.addAll(second);
    }    
}

所以,我想将两个列表合并为一个,但如果第二个列表包含第一个列表,则不会添加.到目前为止,我的方法将它们加在一起.

import java.util.ArrayList;

public class Variance {
// Copy here sum from exercise 63 
public static int sum(ArrayList<Integer> list) {
    int sum = 0;        
    for(int i=0; i<list.size(); i++ ){
        sum = sum + list.get(i) ;
    }
    return sum;
}

// Copy here average from exercise 64 
public static double average(ArrayList<Integer> list) {  
    double average = sum(list)/list.size();
    return average;
}

public static double variance(ArrayList<Integer> list) {
    // write code here
   double sumMinusAverage = sum(list) - average(list);
   return sumMinusAverage * sumMinusAverage / (list.size()-1); …

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;
    }
}

如何在字符串中添加字符,我试过这个,但是我收到了这个错误:

"线程中的异常"主"java.lang.StringIndexOutOfBoundsException:字符串索引超出范围:-414383904".