问为什么这段代码不生成随机代码？

EN

import java.util.ArrayList;
import java.util.Random;

public class Generator{
//9352141NTBG1223

public static void main(String[] args) {
    ArrayList<Integer> intArray = new ArrayList<Integer>();
    ArrayList<Integer> int2Array = new ArrayList<Integer>();
    ArrayList<Character> charArray = new ArrayList<Character>();

    int one = 0;
    int two = 0;
    int three = 0;
    int four = 0;
    int five = 0;
    int six = 0;
    int seven = 0;
    int N_one = 0;
    int N_two = 0;
    int N_three = 0;
    int N_four = 0;
    Character Middle1 = 'A';
    Character Middle2 = 'A';
    Character Middle3 = 'A';
    Character Middle4 = 'A';

    Random gen1 = new Random();

    charArray.add(Middle1);
    charArray.add(Middle2);
    charArray.add(Middle3);
    charArray.add(Middle4);
    intArray.add(one);
    intArray.add(two);
    intArray.add(three);
    intArray.add(four);
    intArray.add(five);
    intArray.add(six);
    intArray.add(seven);
    int2Array.add(N_one);
    int2Array.add(N_two);
    int2Array.add(N_three);
    int2Array.add(N_four);

    for(int i: intArray) {
    int k = gen1.nextInt(10);
    i = k;
    }
    for(int i: int2Array) {
    int k = gen1.nextInt(10);
    i = k;
    }
    for(char i: charArray) {
        int b = gen1.nextInt(20);
        switch (b) {
        case 1: i = 'H'; break;
        case 2: i = 'R'; break;
        case 3: i = 'F'; break;
        case 4: i = 'Y'; break;
        case 5: i = 'U'; break;
        case 6: i = 'Q'; break;
        case 7: i = 'T'; break;
        case 8: i = 'N'; break;
        case 9: i = 'B'; break;
        case 10: i = 'L'; break;
        case 11: i = 'K'; break;
        case 12: i = 'P'; break;
        case 13: i = 'I'; break;
        case 14: i = 'Z'; break;
        case 15: i = 'X'; break;
        case 16: i = 'V'; break;
        case 17: i = 'C'; break;
        case 18: i = 'E'; break;
        case 19: i = 'M'; break;
        }
    }
    System.out.print("Generated Code: ");
    for(int i: intArray) {
    System.out.print(i);
    }
    for(char i: charArray) {
    System.out.print(i);
    }
    for(int i: int2Array) {
    System.out.print(i);
    }
}

  }