selecting a random char in a string in java with a certain method

Question

I have to select and return 1 random character out of a string using this method (separate from main method):

public static char selectAChar(String s)

I'm not sure how to select the random variable, and not sure if i should use a for loop. everything I've tried I couldn't get it to return the right variable type.

EDIT: heres the coding i have so far

public static void main(String args[])
{
    Scanner kbd = new Scanner (System.in);

    System.out.println("Enter a string: ");
    String s = kbd.next();

    selectAChar(s);
}



public  static  char selectAChar(String s)
{


}

i tried something using this for loop for(int i = 0; i < s.length(); i++) but i can't figure out how to choose a random character and return it.

would you have to generate the random number and assign it into an int and then use charAt and locate the random int? — kiffffffkroker, Feb 14 '15 at 04:26

shirrine · Accepted Answer · 2015-02-14T04:31:58.397

3

public static char selectAChar(String s){

    Random random = new Random();
    int index = random.nextInt(s.length());
    return s.charAt(index);

}

edited Feb 14 '15 at 04:31

answered Feb 14 '15 at 04:26

shirrine

403
3
6

how would you print out the random character? – kiffffffkroker Feb 14 '15 at 04:33
For my unit testing I did... String string = "hello world"; System.out.println(selectAChar(string)); Is that what you mean? – shirrine Feb 14 '15 at 04:35
With your example, you would call System.out.println(selectAChar(s)); in your main method. – shirrine Feb 14 '15 at 04:37
yeah, sorry. i was trying to do that and i just had a typo. thanks a lot for your help – kiffffffkroker Feb 14 '15 at 04:38

score 1 · Answer 2 · answered Feb 14 '15 at 04:37

There are at least two ways to generate a random number between 0 and a number (exclusive), one is using a call to Random.nextInt(int) the Javadoc reads in part returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive) and String.charAt(int) the Javadoc says (in part) returns the char value at the specified index.

static Random rand = new Random();
public static char selectAChar(String s) {
    return s.charAt(rand.nextInt(s.length()));
}

For a second way you might use String.toCharArray() and Math.random() like

public static char selectAChar(String s) {
    return s.toCharArray()[(int) (Math.random() * s.length())];
}

And of course, you could use (the somewhat warty) toCharArray()[int] and charAt(int) with either method.

Since you are returning a value, your caller should save it

char ch = selectAChar(s);

And then you might format the input String and print the random char like

System.out.printf("'%s' %c%n", s, ch);

selecting a random char in a string in java with a certain method

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