Task: Password generator
C++: #include <iostream>
#include <string>
#include <algorithm>
#include <ctime>

const std::string CHR[] = { "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "abcdefghijklmnopqrstuvwxyz", 
                            "0123456789", "!\"#$%&'()*+,-./:;<=>?@[]^_{|}~" };
const std::string UNS = "O0l1I5S2Z";

std::string createPW( int len, bool safe ) {
    std::string pw;
    char t;
    for( int x = 0; x < len; x += 4 ) {
        for( int y = x; y < x + 4 && y < len; y++ ) {
            do {
                t = CHR[y % 4].at( rand() % CHR[y % 4].size() );
            } while( safe && UNS.find( t ) != UNS.npos );
            pw.append( 1, t );
        }
    }
    std::random_shuffle( pw.begin(), pw.end() );
    return pw;
}
void generate( int len, int count, bool safe ) {
    for( int c = 0; c < count; c++ ) {
        std::cout << createPW( len, safe ) << "\n";
    }
    std::cout << "\n\n";
}
int main( int argc, char* argv[] ){
    if( argv[1][1] == '?' || argc < 5 ) {
        std::cout << "Syntax: PWGEN length count safe seed /?\n"
                     "length:\tthe length of the password(min 4)\n"
                     "count:\thow many passwords should be generated\n"
                     "safe:\t1 will exclude visually similar characters, 0 won't\n"
                     "seed:\tnumber to seed the random generator or 0\n"
                     "/?\tthis text\n\n";
    } else {
        int l = atoi( argv[1] ),
            c = atoi( argv[2] ),
            e = atoi( argv[3] ), 
            s = atoi( argv[4] );
        if( l < 4 ) {
            std::cout << "Passwords must be at least 4 characters long.\n\n";
        } else {
            if (s == 0) {
               std::srand( time( NULL ) );
            } else {
               std::srand( unsigned( s ) );
            }
            generate( l, c, e != 0 );
        }
    }
    return 0;   
}

Java: import java.util.*;

public class PasswordGenerator {
    final static Random rand = new Random();

    public static void main(String[] args) {
        int num, len;

        try {
            if (args.length != 2)
                throw new IllegalArgumentException();

            len = Integer.parseInt(args[0]);
            if (len < 4 || len > 16)
                throw new IllegalArgumentException();

            num = Integer.parseInt(args[1]);
            if (num < 1 || num > 10)
                throw new IllegalArgumentException();

            for (String pw : generatePasswords(num, len))
                System.out.println(pw);

        } catch (IllegalArgumentException e) {
            String s = "Provide the length of the passwords (min 4, max 16) you "
                    + "want to generate,\nand how many (min 1, max 10)";
            System.out.println(s);
        }
    }

    private static List<String> generatePasswords(int num, int len) {
        final String s = "!\"#$%&'()*+,-./:;<=>?@[]^_{|}~";

        List<String> result = new ArrayList<>();

        for (int i = 0; i < num; i++) {
            StringBuilder sb = new StringBuilder();
            sb.append(s.charAt(rand.nextInt(s.length())));
            sb.append((char) (rand.nextInt(10) + '0'));
            sb.append((char) (rand.nextInt(26) + 'a'));
            sb.append((char) (rand.nextInt(26) + 'A'));

            for (int j = 4; j < len; j++) {
                int r = rand.nextInt(93) + '!';
                if (r == 92 || r == 96) {
                    j--;
                } else {
                    sb.append((char) r);
                }
            }
            result.add(shuffle(sb));
        }
        return result;
    }

    public static String shuffle(StringBuilder sb) {
        int len = sb.length();
        for (int i = len - 1; i > 0; i--) {
            int r = rand.nextInt(i);
            char tmp = sb.charAt(i);
            sb.setCharAt(i, sb.charAt(r));
            sb.setCharAt(r, tmp);
        }
        return sb.toString();
    }
}