Android random string generator

Question

I have a problem. I want to draw a random String something like this aXcFg3s2. What i doing bad ? How change my random()

private String random;
private String charsEntered;
private EditText et;
private Button ok;
CaptchaInterface.OnCorrectListener mCorrectListener;

public void setOnCorrectListener(CaptchaInterface.OnCorrectListener listener) {
    mCorrectListener = listener;
}

public TextCaptcha(Context context) {
    super(context);
    getWindow().requestFeature(Window.FEATURE_NO_TITLE);
}

public static String random() {
    Random generator = new Random();
    String x = (String) (generator.nextInt(96) + 32);
    return x;
}

public void onCreate(Bundle icicle) {
    setContentView(R.layout.main);
    random = random();
    TextView display = (TextView) findViewById(R.id.textView1);
    display.setText("Random Number: " + random); // Show the random number
    et = (EditText) findViewById(R.id.etNumbers);
    ok = (Button) findViewById(R.id.button1);
    ok.setOnClickListener(this);

}

public void onClick(View arg0) {
    // TODO Auto-generated method stub
    try {
        charsEntered = et.getText().toString();
    } catch (NumberFormatException nfe) {
        Toast.makeText(et.getContext(), "Bla bla bla",
                Toast.LENGTH_LONG).show();
    }

    if (random == charsEntered) {
        Toast.makeText(et.getContext(), "Good!", Toast.LENGTH_LONG).show();
    } else {
        Toast.makeText(et.getContext(), "Bad!", Toast.LENGTH_LONG).show();
    }
}

Answer 1

the problem is that you've handled only a single character instead of using a loop.

you can create an array of characters which has all of the characters that you wish to allow to be in the random string , then in a loop take a random position from the array and add append it to a stringBuilder . in the end , convert the stringBuilder to a string.

---

EDIT: here's the simple algorithm i've suggested:

private static final String ALLOWED_CHARACTERS ="0123456789qwertyuiopasdfghjklzxcvbnm";  private static String getRandomString(final int sizeOfRandomString)   {   final Random random=new Random();   final StringBuilder sb=new StringBuilder(sizeOfRandomString);   for(int i=0;i<sizeOfRandomString;++i)     sb.append(ALLOWED_CHARACTERS.charAt(random.nextInt(ALLOWED_CHARACTERS.length())));   return sb.toString();   } 

and on Kotlin:

companion object {     private val ALLOWED_CHARACTERS = "0123456789qwertyuiopasdfghjklzxcvbnm" }  private fun getRandomString(sizeOfRandomString: Int): String {     val random = Random()     val sb = StringBuilder(sizeOfRandomString)     for (i in 0 until sizeOfRandomString)         sb.append(ALLOWED_CHARACTERS[random.nextInt(ALLOWED_CHARACTERS.length)])     return sb.toString() } 

Answer 2

There are a few things wrong with your code.

You cannot cast from an int to a string. Cast it to a char instead. This however will only give you a single char so instead you could generate a random number for the length of your string. Then run a for loop to generate random chars. You can define a StringBuilder as well and add the chars to that, then get your random string using the toString() method

example:

public static String random() {     Random generator = new Random();     StringBuilder randomStringBuilder = new StringBuilder();     int randomLength = generator.nextInt(MAX_LENGTH);     char tempChar;     for (int i = 0; i < randomLength; i++){         tempChar = (char) (generator.nextInt(96) + 32);         randomStringBuilder.append(tempChar);     }     return randomStringBuilder.toString(); } 

Also, you should use random.compareTo() rather than ==

Answer 3

You need to import UUID. Here is the code

import java.util.UUID;

id = UUID.randomUUID().toString();