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@vpiotr vpiotr/PassGen.java
Created Jan 14, 2017

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package passgen;
import java.util.Random;
import java.util.Scanner;
/**
* Exercise 37 from "Exercises for programmers".
* @author Piotr Likus
*/
public class PassGen {
static Random rnd = new Random();
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("--- Password generator ---");
int passLen = readInt(sc, "What's the minimum length?");
int specCount = readInt(sc, "How many special characters?");
int numCount = readInt(sc, "How many numbers?");
int cnt = 5;
while(cnt-- > 0) {
String passwd = generatePassword(passLen, specCount, numCount);
System.out.println("Your password is:"+passwd);
}
}
private static int readInt(Scanner sc, String prompt) {
System.out.println(prompt);
return sc.nextInt();
}
private static String generatePassword(int passLen, int specCount, int numCount) {
final String specialChars = "!@#$%^&*()-=_+\\|";
final String digits = "0123456789";
final String alpha = "abcdefghijklmnopqrstvuwyzABCDEFGHIJKLMNOPQRSTVUWXYZ";
StringBuilder res = new StringBuilder();
int specAdded = 0;
int numAdded = 0;
while(res.length() < passLen) {
CharType ct = PassGen.randomCharType();
switch(ct) {
case SPECIAL: {
if (specAdded < specCount) {
res.append(randomChar(specialChars));
specAdded++;
break;
}
}
case DIGIT: {
if (numAdded < numCount) {
res.append(randomChar(digits));
numAdded++;
break;
}
}
default: {
res.append(randomChar(alpha));
}
}
}
return res.toString();
}
private static CharType randomCharType() {
int idx = rnd.nextInt(3);
switch(idx) {
case 0: return CharType.SPECIAL;
case 1: return CharType.DIGIT;
default:
return CharType.ALPHA;
}
}
private static char randomChar(String text) {
int idx = rnd.nextInt(text.length());
return text.charAt(idx);
}
private enum CharType {
SPECIAL,
DIGIT,
ALPHA
}
}
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