Help for creating a random string

Question

I need to create a random string that should be between 6 to 10 in length, but sometimes it only generates 3 to 5 in length. Here is my code. Can someone find out the problem ?: (

            int lengthOfName = (int)(Math.random() * 4) + 6;
        String name = "";
        /* randomly choosing a name*/
        for (int j = 0; j <= lengthOfName; j++) {
            int freq = (int)(Math.random() * 100) + 1;
            if(freq <= 6){
                name += "a";
            }if(freq == 7 && freq == 8){
                name += "b";
            }if(freq >= 9 && freq <= 11){
                name += "c";
            }if(freq >= 12 && freq <= 15){
                name += "d";
            }if(freq >= 16 && freq <= 25){
                name += "e";                        
            }if(freq == 26 && freq == 27){
                name += "f";
            }if(freq == 28 && freq == 29){
                name += "g";
            }if(freq >= 30 && freq <= 33){
                name += "h";
            }if(freq >= 34 && freq <= 48){
                name += "i";
            }if(freq == 49 && freq == 50){
                name += "j";
            }if(freq >= 51 && freq <= 55){
                name += "k";
            }if(freq >= 56 && freq <= 60){
                name += "l";
            }if(freq == 61 && freq == 62){
                name += "m";
            }if(freq >= 63 && freq <= 70){
                name += "n";
            }if(freq >= 71 && freq <= 75){
                name += "o";
            }if(freq == 76 && freq == 77){
                name += "p";
            }if(freq == 78){
                name += "q";
            }if(freq >= 79 && freq <= 84){
                name += "r";
            }if(freq == 85 && freq == 86){
                name += "s";
            }if(freq == 87 && freq == 88){
                name += "t";
            }if(freq >= 89 && freq <= 93){
                name += "u";
            }if(freq == 94){
                name += "v";
            }if(freq == 95 && freq == 96){
                name += "w";
            }if(freq == 97){
                name += "x";
            }if(freq == 98 && freq == 99){
                name += "y";
            }if(freq == 100){
                name += "z";
            }
        }

Answer 1

Sorry, but the code is too poorly written to be saved. I recommend something like this.

    Random r = new Random(); // just create one and keep it around
    String alphabet = "abcdefghijklmnopqrstuvwxyz";

    final int N = 10;
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < N; i++) {
        sb.append(alphabet.charAt(r.nextInt(alphabet.length())));
    }
    String randomName = sb.toString();

    System.out.println(randomName);

Key points:

• Use java.util.Randomin particular nextInt(int n)to get random intin a given range
  • No funky formulas needed
• When building a line in a loop, use StringBuilder.
• Use the string of the alphabet and charAtto index its letters.

API Links

• java.util.Random
  • int nextInt(int n)
    • int 0 () ()
• StringBuilder - .

• String vs StringBuilder (#)
• String, StringBuffer StringBuilder (Java)

---

, .

• String +=
• for (int j = 0; j <= lengthOfName; j++)
• freq == 7 && freq == 8 -
• !
  • , -

, , Java. codingbat.com ; , , , , , . , , ..

---

:

• String alphabet = "aab"; a , b
• alphabet
  • ( , )

Answer 2

, if(freq == X && freq == X+1), false.

, || (OR)

Answer 3

:

if(freq == 28 && freq == 29) { ... }

Java, , freq equals to 28 freq equals to 29. . OR:

if(freq == 28 || freq == 29) { ... }

, , freq , , .

Answer 4

:

import java.util.Random;

Random gen = new Random(474587); //put in random seed
int min = 6;
int max = 10;

// we want 20 random strings 
for(int i=0; i < 20; i++){
 int len = min+gen.nextInt(max-min+1);
 StringBuilder s = new StringBuilder(len);
 while(s.length() < len){
  //97 is ASCII for character 'a', and 26 is number of alphabets
  s.append((char)(97+gen.nextInt(26)));     
 }

System.out.println(s.toString());
}

---

:

zqwloh
jefcso
spcnhxyyk
tzlobaukn
keyxkn
cllhsxybz
ieaudei
bolfzqlxrl
scpfcbztyh
thkfrybffe
nbspabxjh

Answer 5

, .

if (freq == 49 & freq == 50) {               name + = "j";

.

Answer 6

, , , , .

, , , , - . 10 6 10 :

import java.util.Random;


public class Stuff {
public static void main(String[] args) {

    Random rand = new Random();
    int[] freqs = new int[] {6,8,11,15,25,27,29,33,48,50,55,60,62,70,75,77,78,84,86,88,93,94,96,97,99,100};

    int numWords = 10;
    for(int i = 0; i<numWords; i++)
    {
        String word = "";
        int numLetters = 6 + rand.nextInt(5);
        for(int j = 0; j<numLetters; j++)
        {
            int freq = rand.nextInt(100) + 1;
            int index = 0;
            while(freqs[index] < freq) index++;
            word = word + (char)(97 + index );              
        }
        System.out.println(word);
    }
}

, - , ?

JB

Answer 7

, "" ( ) , , :

private static final Random random = new Random();

public static String generateRandomString() {
    return new BigInteger((4 + random.nextInt(3)) * 8, random).toString(36);
}

, [a-z0-9] 6 ~ 10 ().

Answer 8

import java.util.*;
public class RandomString6to10

{
    public static void main(String[] args)
    {
        Random rnd = new Random();
        Scanner scan = new Scanner (System.in);
        String alphabets = "abcdefghijklmnopqrstuvwxyz";
        int min1 = rnd.nextInt(5) + 6;
        int min2 = rnd.nextInt(3) + 3;
        System.out.println("How many strings do you want?");
        int x = scan.nextInt();

        for ( int i = 0; i < x; i++)
        {
/* because you didn't tell us when should the generator decide to choose 6-10 or 3-5 
so I made it random */

            if (rnd.nextBoolean()) 
            { 
                min1 = rnd.nextInt(5) + 6;
                for (int t=0; t < min1; t++)
                {
                    int randomString1 = rnd.nextInt(alphabets.length());
                    System.out.print(alphabets.charAt(randomString1));
                }
                System.out.println();
            }
            else 
            {
                min2 = rnd.nextInt(3) + 3;
                for (int j=0; j < min2; j++)
                {
                    int randomString2 = rnd.nextInt(alphabets.length());
                    System.out.print(alphabets.charAt(randomString2));
                }
                System.out.println();

            }
        }
    }
}