how to return random string Arrray Java

Question

I am very new to Java, so this could seem too easy for most people....Is this completely wrong? My question is how to write a method selectRandom(String[] names), which returns a randomly selected name from the given array.

Each name should be selected with equal probability.

public static String selectRandom(String[] names)    
{    
    String num = names[0]; 
    int[]newArray = new int[names.length];
    for(int i =0; i<names.length;i++)
    {
      Random r = new Random();
      int ranNum= r.nextInt(names.length)+1;
      num = names[ranNum];
    }
    return num;  
}

You don't need to have a loop there. Just select the random index and return the corresponding string. — Shashwat
– Shashwat, Commented Oct 5, 2012 at 8:58
The steps: select a number randomly that is less than array length, the return the array element? Can you translate this to code? — nhahtdh
– nhahtdh, Commented Oct 5, 2012 at 9:00
i think the main problem here is not how to get a random. since OP mentioned Each name should be selected with equal probability. I think he needs a uniformed random function. I don't think Random in java core library is uniformed. — Kent
– Kent, Commented Oct 5, 2012 at 9:02
@Kent int java.util.Random.nextInt(int n): Returns a new pseudo-random integer value which is uniformly distributed between 0 (inclusively) and n (exclusively) — pankar
– pankar, Commented Oct 5, 2012 at 9:07
@pankar checked the doc again. Returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive).. u r right. thx. I think I was abit mixing up with real-random... — Kent
– Kent, Commented Oct 5, 2012 at 9:13

FThompson · Accepted Answer · 2012-10-05 15:17:22Z

5

You can simply generate a random number up to the array size, and get the value at that index.

public static String selectRandom(String[] names) {
    if (name != null && names.length > 0) {
        Random r = new Random();
        return names[r.nextInt(names.length)];
    }
    return null;
}

edited Oct 5, 2012 at 15:17

answered Oct 5, 2012 at 9:00

FThompson

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4 Comments

Subhrajyoti Majumder Over a year ago

you should add null check also otherwise if (names.length > 0) it may populate nullpointer exception.

Kunu Over a year ago

@Vulcan Can you please tell me how can I choose a random string value from an array and also I want some other string every time. I mean if I don't want to repeat the same string value, what's modification I need in this code .

FThompson Over a year ago

@Kunu Create another array of Strings (or booleans) and keep track of which Strings you've randomly picked already.

Kunu Over a year ago

@Vulcan I was also thinking about that, but thought it would be wise to ask others first so if there any direct method exist in Random function I could do it easily. Thanks for your reply.

Russell Gutierrez · Accepted Answer · 2012-10-05 09:01:15Z

4

public static String selectRandom(String[] names)    
{    
      Random r = new Random();
      int ranNum= r.nextInt(names.length);
      return names[ranNum];

}

You don't need most of the codes inside your method. Maybe you should try something like this?

answered Oct 5, 2012 at 9:01

Russell Gutierrez

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2 Comments

Subhrajyoti Majumder Over a year ago

it may generate NullPointerException too.

Kunu Over a year ago

@Russell Gutierrez Can you please tell me how can I choose a random string value from an array and also I want some other string every time. I mean if I don't want to repeat the same string value, what's modification I need in this code .

Emil · Accepted Answer · 2012-10-05 09:03:27Z

0

Randomly choose an index and return the corresponding String in names. There is a Random class to do get random numbers in java. Also check nextInt method.

public static String selectRandom(String[] names)    
{    
   Random rand = new Random();
   int index = rand.nextInt(names.length);
   return names[index];
}

answered Oct 5, 2012 at 9:03

Emil

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