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I want to create a program that generates a random password and asks the user to guess the password

I am creating a program that generates a random password and asks the user to guess the generated password.
The problem I'm facing now is how to compare the generated password to the inputted password
My program compares the length of both passwords, but I don't know any possible way to compare both passwords to see if they're the same or not
The program has to compare both passwords and after three attempts, the program has to output the generated password
The code below is my program
final static Scanner in = new Scanner(System.in);
public static String method(int len){
String ASCII = "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z a b c d e f g h i j k l m n o p q r s t u v w x y z";
int count =0;
int rand;
System.out.println("Guess the generated password");
String key = in.nextLine();
for(int i=0;i<key.length();i++){
count++;
}
SecureRandom sr = new SecureRandom();
StringBuilder sb = new StringBuilder();
for(int i =0;i<len;i++){
rand= sr.nextInt(ASCII.length());
sb.append(ASCII.charAt(rand));
}
for(int i=0;i<3;i++){
if(len!=count){
System.out.println("The length of the random generated password is "+ len+ " and the length of the password inserted is " + count);
System.out.println("The length of the generated password and the length of the inserted password varies. Please try again...");
System.out.println("Guess the generated password again");
key = in.nextLine();
}
}
return sb.toString();
}
public static void main(String[] args) {
Random r = new Random();
int len;
len = r.nextInt(1, 8);
System.out.println("length :" + len);
System.out.println(method( len));
}
}

You have made some strides in your coding since this post was originally placed. Based on your newest code shown below (from the post you deleted):
final static Scanner in = new Scanner(System.in);
public static String method(int len) {
//Create a variable to hold the ASCII character
String ASCII = "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z a b c d e f g h i j k l m n o p q r s t u v w x y z";
int count = 0;
int rand;
System.out.println("Guess the generated password");
String key = in .nextLine();
for (int i = 0; i < key.length(); i++) {
count++;
}
SecureRandom sr = new SecureRandom();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < len; i++) {
rand = sr.nextInt(ASCII.length());
sb.append(ASCII.charAt(rand));
}
for (int i = 1; i < 3; i++) {
while (len != key.length()) {
System.out.println("Length do not correspond please try again");
key = in .nextLine();
}
if (len == key.length() && !sb.toString().equals(key)) {
System.out.println("Length correspond but passwords differ, Try again");
key = in .nextLine();
}
}
System.out.print("The correct password is: ");
return sb.toString();
}
public static void main(String args[]) {
// Create a random length generator
Random r = new Random();
int len;
len = r.nextInt(1, 7);
System.out.println("lungezza :" + len);
System.out.println(method(len));
}
When generating a random number within a specific range like 1 inclusive to 7 inclusive then do it this way:
// int len = rand.nextInt((max - min) + 1) + min; thus...
int len = new Random().nextInt((7 - 1) + 1) + 1;
Don't add a bunch of whitespaces in your ASCII String variable. Consider not having whitespaces at all or if you have to, just provide one between the Upper and lower letters, for example:
String ASCII = "ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz";
I say this because potentially, there is a good chance your random password generation could create a password that is all whitespaces which really isn't a password at all.
Also, I know your compiler isn't complaining but readers of your code will....consider using proper naming conventions for your variables, etc. ASCII should be ascii or even aSCII unless it is going to be a class Field variable which it is not. It is currently considered a method local variable. You actually did this correctly in this older post.
You can not guess an auto-generated password if that auto-generated password has not been generated yet. The code which auto-generates the password to guess is currently after the first prompt which asks you to supply what it is.
Move the code that generates the password above the code that asks the first prompt of what that password might be, for example:
//Create a variable to hold the ASCII characters
String ascii = "ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz";
// Generate the secret password to guess...
SecureRandom sr = new SecureRandom();
StringBuilder sb = new StringBuilder("");
int rand;
for (int i = 0; i < len; i++) {
rand = sr.nextInt(ascii.length());
sb.append(ascii.charAt(rand));
}
// Guess the password...
int count = 0;
System.out.print("Guess the generated password: -> ");
String key = in .nextLine();
for (int i = 0; i < key.length(); i++) {
count++;
}
This for loop under the first Guess prompt:
int count = 0;
System.out.print("Guess the generated password: -> ");
String key = in.nextLine();
for (int i = 0; i < key.length(); i++) {
count++;
}
is not required. All it does is count the number of characters contained within the first password guess. Ironically, you already know this by just using the key.length() method. You don't use the count variable for anything anyways so you may as well just get rid of all that:
// Guess the password (3 guesses)...
System.out.print("Guess the generated password: -> ");
String key = in .nextLine();
for (int i = 1; i < 3; i++) {
while (len != key.length()) {
System.out.println("Lengths do not correspond please try again");
key = in .nextLine();
}
if (len == key.length() && !sb.toString().equals(key)) {
System.out.println("Lengths correspond but passwords differ, Try again");
key = in .nextLine();
}
}
System.out.print("The correct password is: ");
return sb.toString();
In reality, you only need one prompt and it's always nice to validate the User's input. Here is an alternative way to do this:
private final static Scanner in = new Scanner(System.in);
private static int numberOfGuessesAllowed = 3;
private static boolean correct = false;
public static void main(String args[]) {
// Create a random length generator
Random r = new Random();
int len = r.nextInt((7 - 1) + 1) + 1;
System.out.println("Password to guess contains " + len + " characters.");
System.out.println("You have " + numberOfGuessesAllowed + " attempts to guess it right!");
System.out.println(method(len));
}
public static String method(int len) {
//Create a variable to hold the ASCII characters
String ascii = "ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz";
// Generate the secret password to guess...
SecureRandom sr = new SecureRandom();
StringBuilder sb = new StringBuilder("");
int rand;
for (int i = 0; i < len; i++) {
rand = sr.nextInt(ascii.length());
sb.append(ascii.charAt(rand));
}
String secretPassword = sb.toString();
// Guess the password...
String key = "";
while (key.isEmpty() && numberOfGuessesAllowed > 0) {
System.out.print("Guess the generated password (q to quit): -> ");
key = in .nextLine().trim();
if (key.equalsIgnoreCase("q")) {
return "Quitting! Bye-Bye.";
}
if (key.isEmpty()) {
System.out.println("Invalid Entry! Try again...\n");
}
else if (secretPassword.equals(key)) {
correct = true;
break;
}
else if (len != key.length()) {
numberOfGuessesAllowed--;
System.out.println("Lengths do not correspond! Please try again.\n");
key = "";
}
else if (len == key.length() && !secretPassword.equals(key)) {
numberOfGuessesAllowed--;
System.out.println("Lengths correspond but passwords differ, Try again\n");
key = "";
}
}
if (correct) {
System.out.print("You guessed it! The password is: ");
}
else {
System.out.print("You couldn't do it! The correct password is: ");
}
return secretPassword;
}

Problem with this error : Exception in thread "main" java.lang.NumberFormatException: For input string: ""

This is the problem wherein, we will subtract two numbers using 9's complement.
import java.io.*;
public class NinesComplement {
public static void main(String[] args)throws java.io.IOException {
java.io.BufferedReader br = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
while (true) {
System.out.print("Enter Minuend: ");
int min = Integer.parseInt(br.readLine());
System.out.print("Enter Subtrahend: ");
String sub = br.readLine();
int max = Integer.toString(min).length();
for (int i = 0; sub.length() < max; i++) {
sub = 0 + sub;
}
String [] subArr = sub.split("");
int[] num = new int[subArr.length];
for (int i = 0; i < subArr.length; i++) {
num[i] = Integer.parseInt(subArr[i]);
}
int[] n = new int[num.length];
for (int i = 0; i < num.length; i++) {
for (int ii = 0; num[i] < 9; ii++) {
num[i]++;
n[i]++;
}
}
String str = "";
for (int i = 0; i < num.length; i++) {
str += Integer.parseInt(Integer.toString(n[i]));
}
int add = Integer.parseInt(str);
String ans = Integer.toString(min + add);
if (ans.length() > max) {
String temp1 = ans.substring(0, 1);
String temp2 = ans.substring(1, ans.length());
int fin = Integer.parseInt(temp2) + Integer.parseInt(temp1);
System.out.println("Answer: " + fin);
} else if (ans.startsWith("9") && ans.endsWith("9")) {
System.out.println("Answer: 0");
}
System.out.print("Do you want to try again? \n[y][n]: ");
String choice = br.readLine();
if (choice.equals("n")) {
System.out.println("Thank you!!!");
System.exit(0);
}
}
}
}
Exception in thread "main" java.lang.NumberFormatException: For input
string: ""

You're just trying to parse an empty string into a number. You should always validate user input before trying to use it :).
Add a pre-condition (just an if statement check) before using the input and print a nice message to the user if the input was bad, and just go back to waiting for more good input.
Also, to debug this issue, just make your life easier and add some print statements surrounded by quotes before you try and use the user input so you can see it.

Java: Printing trailing spaces

I'm a beginner in Java and working on a code that first requires user to enter total number of integers and next the integers themselves. Example input is:
4
1 4 3 2
The code will need to reverse the second input to the following:
2 3 4 1
My solution is as follow:
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
int arr[] = new int[n];
for(int arr_i=0; arr_i < n; arr_i++){
arr[arr_i] = in.nextInt();
}
for(int reverse_i=n-1; reverse_i>=0; reverse_i--){
System.out.print(arr[reverse_i]);
if(reverse_i != 0){System.out.print(" ");}
}
}
My question is related to the code to add a blank space " " in between the printed numbers. I wonder what other way I can use to get this done? Any suggestion is appreciated, thank you.

The easy way to reverse a string is using the StringBuilder class:
One option is to remove the spaces at the end of the string eg. remove last char
package stackoverflow.main;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
StringBuilder sb = new StringBuilder();
for(int arr_i = 0; arr_i < n; arr_i++){
sb.append(in.nextInt());
sb.append(" ");
}
sb.deleteCharAt(sb.length() - 1);
String normal = sb.toString();
String reversed = sb.reverse().toString();
System.out.println("normal: " + normal);
System.out.println("reversed: " + reversed);
}
}
Another option is to check whether you are at the last arr_i of your loop.
If so, then don't add a space
package stackoverflow.main;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
StringBuilder sb = new StringBuilder();
for(int arr_i = 0; arr_i < n; arr_i++){
sb.append(in.nextInt());
if (arr_i != 3
sb.append(" ");
}
String normal = sb.toString();
String reversed = sb.reverse().toString();
System.out.println("normal: " + normal);
System.out.println("reversed: " + reversed);
}
}

First reverse the array and then print it with a for loop.
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
int arr[] = new int[n];
for(int arr_i=0; arr_i < n; arr_i++)
{
arr[arr_i] = in.nextInt();
}
for(int i = 0; i < arr.length / 2; i++)
{
int temp = arr[i];
arr[i] = arr[arr.length - i - 1];
arr[arr.length - i - 1] = temp;
}
for(int i = 0; i < arr.length; i++)
{
System.out.print(arr[i]+" ");
}
}
}

It is all about output formatting. You may use this examples and become familiar with all possible approaches.
Your code can be improved in next two ways :
1) Use \t instead of Empty Space (\t is a tabulation)
2) Create a constant with output format like this private static final String output = "%d " and use it in output line like this : String.format(output, number) where number is your number that should be printed.

I'm lost, where do I go from here?

My teacher asked that we use the ASCII characters from 33 to 127 to generate a password that is n length. I got lost and am not sure where to go from here. This is what I have so far:
import java.util.*;
public class PasswordGenerator {
public static void main(String[]args){
Random random = new Random();
Scanner input = new Scanner(System.in);
System.out.print("Enter password length: ");
int length = input.nextInt();
StringBuilder password = new StringBuilder(length);
int count = random.nextInt(127-33+1)-33'
if(length<0) {
System.out.println(Invalid password length: "+length);
}
else {
for(int i = 33; i<126+1; i++) {

You are not using the Random object correctly, since as it is, you can generate negative numbers.
This is one way to implement what you are describing:
if(length<0) /*handle error*/;
StringBuilder password = new StringBuilder();
for(int i = 0; i < length ; i++) {
password.append((char) (random.nextInt(127-33+1)+33));
}

Here's the updated version:
public static void main(String[] args) {
Random random = new Random();
try(Scanner input = new Scanner(System.in);){
System.out.print("Enter password length: ");
int length = input.nextInt();
StringBuilder password = new StringBuilder();
if (length < 0) {
System.out.println("Invalid password length: " + length);
}
for(int i = 0 ; i < length ; i++){
password.append((char) (random.nextInt(127-33) + 33));
}
System.out.println(password.toString());
}
}
changes:
Count variable was not needed.
Length was not being utilized.
Scanner object was not closed, causing a resource leak.

Reading int, double and strings and ignore tokens

12.9 ; I # 13 jav
3.8 ; can # 6 aru
4.0 ; read # 109 les
The program is supposed to read this in as a string and then add all the doubles, integers, and then to add the first string together and the last string together. So the program should provide
Double total : 20.7
Integer total : 128
Line : I can read
Word: javarules
This is what I have so far , I know that I have to use scanner to skip over the tokens .
public class Test {
public static void main (String args[]) throws FileNotFoundException {
Scanner sc = new Scanner(Test4.class.getResourceAsStream("week2inputdata.txt"));
double doubletotal = 0;
int inttotal = 0;
String line = " ";
String word;
Scanner scanLine;
while (sc.hasNextLine()){
scanLine = new Scanner (sc.nextLine());
scanLine.next();
line += sc.hasNextLine();
inttotal += sc.nextInt();
// scanLine = new Scanner (sc.nextLine());
// scanLine.next();
// line += sc.next() + " ";
// inttotal += sc.nextInt();
doubletotal += sc.nextDouble();
}
System.out.println(inttotal);
System.out.println(doubletotal);
System.out.println(line);
}
}

This is rather ugly but it will work,
String[] weirdLookingString = new String[] { "12.9 ; I # 11 jav", "3.8 ; can # 11 aru"
,"4.0 ; read # 109 les" };
double doubleValue = 0.0;
String strValue1 = "";
String strValue2 = "";
int integerValue = 0;
for (int i = 0; i < weirdLookingString.length; i++) {
String array[] = weirdLookingString[i].split("[;\\#]\\s+");
String lastString[] = array[2].split("\\s");
integerValue += Integer.parseInt(lastString[0]);
doubleValue += Double.parseDouble(array[0]);
strValue2 += lastString[1];
strValue1 += array[1];
}
System.out.println("Integer value: " + integerValue);
System.out.println("Double value: " + doubleValue);
System.out.println("Words: " + strValue2);
System.out.println("Line: " + strValue1);
output,
Integer value: 131
Double value: 20.7
Words: javarules
Line: I can read

You can create an arraylist of double, Integers and then create a sb builder for the first set of string and a stringBuilder for the second set of strings.
String line = "12.9 ; I # 13 jav";
String str[] = line.split("[;\\#\\s+]");
StringBuilder sb = new StringBuilder();
StringBuilder sb2 = new StringBuilder();
ArrayList<Double> doubleArray = new ArrayList();
ArrayList<Integer> intArray = new ArrayList();
for(int i =0; i < str.length; i++){
if(i == 0){
doubleArray.add(Double.parseDouble(str[i]));//convert to double and add it to the list
}else if(i == 1){
sb.append(str[i]);
}else if(i == 2){
doubleInt.add(Integer.parseInt(str[i]));//convert it to integer and add to the list
}else if(i == 3){
sb2.append(str[i]);
}
}
you can put everything in a loop so you won't have to rewrite everything. after everything has been added you can build a string using the stringBuilder and add everything using the array from arrayList