Generating a Random sequence

Question

Hello All,
I want some help writing a method which generates a set of 100 numbers with values 0 and 1, but the input should be percent of number of 1's and 0's...I mean if I give 20% for 0's and 80% for 1's then in the generated sequence I should get 20, 0's and 80, 1's...randomly.....hope Iam clear with my question.....please help me
Thanks,
Raghu.

Answer 1

Here is a utility you can use.. you just need to make the call to get the proper random number of ones and pass the size you want.. it returns an array of strings of ones and zero's but you can convert it to whatever type you need.
--John Putnam
import java.util.*;
* <p>Title: ShuffleBits</p>
* <p>Description: example of creating a string of 1's and 0's and shuffling them</p>
* <p>Copyright: Copyright (c) 2003</p>
* @author John Putnam
* May be use freely with inclusion of this copyright notice
* @version 1
public class ShuffleBits
      * method to create an array of strings of 1's and zeros then shuffle them
      * @param numberOfOnes exatly to include (the rest are zero's)
      * @param maxNumberOfBits total number of ones and zeros.
      * @return randomized list of ones and zeros
  public String[]  randBits(int numberOfOnes, int maxNumberOfBits)
       ArrayList bits  = new ArrayList(maxNumberOfBits);
       for(int i=0;i<numberOfOnes;i++) bits.add("1");
       for(int j=0;j<(maxNumberOfBits-numberOfOnes);j++) bits.add("0");
       Collections.shuffle(bits);  //--do the shuffling of order
       Iterator ib = bits.iterator();
       String[] bitsBack = new String[maxNumberOfBits];
          //--pull out the shuffled bits
       int rb = 0;
       while(ib.hasNext()) bitsBack[rb++] = (String)ib.next();
       return bitsBack;
   } //--end randBits
//--------------------------------unit testing main--------------------------------
   public static void main(String[] args)
         ShuffleBits test = new ShuffleBits();
         int numOnes;
         int maxNumber;
         String[] bitsBack = null;
         numOnes = 5;
         maxNumber = 15;
         bitsBack = test.randBits(numOnes,maxNumber);
         System.out.println("\n--Test for #ones: " + numOnes + " max: " + maxNumber);
         for(int i=0;i<maxNumber;i++) System.out.println("--I: " + i + " bit: " + bitsBack);
numOnes = 12;
maxNumber = 15;
bitsBack = test.randBits(numOnes,maxNumber);
System.out.println("\n--Test for #ones: " + numOnes + " max: " + maxNumber);
for(int i=0;i<maxNumber;i++) System.out.println("--I: " + i + " bit: " + bitsBack[i]);
numOnes = 12;
maxNumber = 15;
bitsBack = test.randBits(numOnes,maxNumber);
System.out.println("\n--Test for #ones: " + numOnes + " max: " + maxNumber);
for(int i=0;i<maxNumber;i++) System.out.println("--I: " + i + " bit: " + bitsBack[i]);
numOnes = 12;
maxNumber = 15;
bitsBack = test.randBits(numOnes,maxNumber);
System.out.println("\n--Test for #ones: " + numOnes + " max: " + maxNumber);
for(int i=0;i<maxNumber;i++) System.out.println("--I: " + i + " bit: " + bitsBack[i]);
} //--end main
} //--end shuffle bits
The output was.
--Test for #ones: 5 max: 15
--I: 0 bit: 0
--I: 1 bit: 1
--I: 2 bit: 0
--I: 3 bit: 0
--I: 4 bit: 1
--I: 5 bit: 0
--I: 6 bit: 0
--I: 7 bit: 0
--I: 8 bit: 0
--I: 9 bit: 1
--I: 10 bit: 0
--I: 11 bit: 0
--I: 12 bit: 1
--I: 13 bit: 1
--I: 14 bit: 0
--Test for #ones: 12 max: 15
--I: 0 bit: 1
--I: 1 bit: 1
--I: 2 bit: 0
--I: 3 bit: 0
--I: 4 bit: 1
--I: 5 bit: 1
--I: 6 bit: 0
--I: 7 bit: 1
--I: 8 bit: 1
--I: 9 bit: 1
--I: 10 bit: 1
--I: 11 bit: 1
--I: 12 bit: 1
--I: 13 bit: 1
--I: 14 bit: 1
--Test for #ones: 12 max: 15
--I: 0 bit: 1
--I: 1 bit: 1
--I: 2 bit: 0
--I: 3 bit: 1
--I: 4 bit: 1
--I: 5 bit: 0
--I: 6 bit: 1
--I: 7 bit: 1
--I: 8 bit: 0
--I: 9 bit: 1
--I: 10 bit: 1
--I: 11 bit: 1
--I: 12 bit: 1
--I: 13 bit: 1
--I: 14 bit: 1
--Test for #ones: 12 max: 15
--I: 0 bit: 1
--I: 1 bit: 1
--I: 2 bit: 1
--I: 3 bit: 1
--I: 4 bit: 1
--I: 5 bit: 1
--I: 6 bit: 1
--I: 7 bit: 0
--I: 8 bit: 0
--I: 9 bit: 1
--I: 10 bit: 1
--I: 11 bit: 1
--I: 12 bit: 1
--I: 13 bit: 0
--I: 14 bit: 1
notice the last few are the same sizes but come out in different order.
--John Putnam