Generate random letters and numbers together

Is this homework? If so please tag your question appropriately.

Here is a clue: letters and numbers are all characters, which you could store in an array.

In java you can do char arithmetics. So

'A' + RNG.nextInt(26); 

will return you a random letter between 'A' and 'Z', where RNG is an instance of java.util.Random.

To build the string efficiently. Use a StringBuilder

Not sure if this is homework (it looks like it is), so I'll try to point you in the right direction of a possible approach:

• Recall that a random integer can be any integer X between two other specified integers Y and Z.
• How can you go from a random number to a random CHARacter?
• How could you take a random number between 0 and 13, and turn that into an even number between 0 and 26? An odd number?
• How can you use these ideas/concepts to your advantage for answering this question?

using my library dollar is simple:

@Test public void generateRandomString() { String string = $('a', 'z').shuffle().slice(3).join() + // take 3 random letters $('0', '9').shuffle().slice(3).join(); // take 3 random digits assertThat(string.length(), is(6)); } 

use the random generator function to generate a number in the range [0,26) and add the value of (int)'a' to that, and cast the result back to a char

Generate a set of numbers between 0 - 61 (there are 61 letters for upper and lower, plus digits) and map each to one of [0-9a-zA-Z], then concatenate the whole thing together.

Some basic things you can use:

• an array of all 26 characters in the alphabet and,
• 1 or 2 instances of a random number generator.

I want to generate 6 random characters including 3 random letters followed by 3 random numbers but I can only generate only letters or numbers at one time.

char a = randomLetter(); char b = randomLetter(); char c = randomLetter(); int x = randomNumber(); int y = randomNumber(); int z = randomNumber(); String result = new String()+a+b+c+x+y+z; 

You could have a look at RandomStringUtils, or at least at its source code.

Try with xeger and brics automaton.

import nl.flotsam.xeger.Xeger; import dk.brics.automaton.Automaton; public class RandomizeString{ public String generateRandomString(){ String regex = "[ACEGIKMOQSUWY][BDFHJLNPRTVXZ][A-Z][0-9]{3}"; Xeger generator = new Xeger(regex); String result = generator.generate(); return result; } } 

to understand more, learn Regular Expression.