Generating unique no.'s using random function

Question

Hi,
I'm trying to generate unique values for row and column say from 0-3
and I read some where that if we use random.nextInt() we will get unique values but I'm getting repeated values.I'll appreciate if anyone can help me in this matter.Here's the code:
import java.io.*;
import java.util.*;
import java.lang.*;
public class random{
public static void main(String args[])
int b[]=new int[4];
int c[]=new int[4];
int i;
Date date;
Random random;
date=new Date();
random = new Random(date.getTime());
for(i=0;i<4;i++)
digit = random.nextInt(4);
b=digit;
for(i=0;i<4;i++)
digit = random.nextInt(4);
c[i] = digit;
for(i=0;i<4;i++)
System.out.println("column array is" + c[i]);
for(i=0;i<4;i++)
System.out.println("row array is" + b[i]);
}//end main
}//end class
Thanks
Suneetha.

Answer 1

here is my code for generating a random number but not a unique number. with a big enough number the possibility getting a unique is high so you may modify it to suit you need:
  private void initial_node()
    float Qxyd = -1, Qyzd = -1, Cxyd = -1, Cyzd = -1;
    long seed;
    Q_table = new float[row][col];
    seed = (long)( Math.random() * System.currentTimeMillis() * 100000000 );
    Random rand1 = new Random( seed );
    seed = (long)( Math.random() * System.currentTimeMillis() * 100000000 );
    Random rand2 = new Random( seed );
    seed = (long)( Math.random() * System.currentTimeMillis() * 100000000 );
    Random rand3 = new Random( seed );
    seed = (long)( Math.random() * System.currentTimeMillis() * 100000000 );
    Random rand4 = new Random( seed );
    for( int i = 0; i < row; i++ )
      do
        Qxyd = (float)( rand1.nextFloat() + (float)rand1.nextFloat() / 3 );
      while( Qxyd < 0.35 || Qxyd == -1 );
      Q_table[5] = Math.abs( Qxyd );
do
Qyzd = (float)( rand2.nextFloat() + (float)rand2.nextFloat() / 7 );
while( Qyzd < 0.45 || Qyzd == -1 );
Q_table[i][3] = Math.abs( Qyzd );
do
Cxyd = (float)( rand3.nextFloat() + (float)rand3.nextFloat() / 9 );
while( Cxyd > 0.15 || Cxyd == -1 );
Q_table[i][8] = Math.abs( Cxyd );
do
Cyzd = (float)( rand4.nextFloat() + (float)rand4.nextFloat() / 11 );
while( Cyzd > 0.10 || Cyzd == -1 );
Q_table[i][9] = Math.abs( Cyzd );