Random number generation

[chandanapapa]

Can anyone pls help me to generate random numbers without using any API???

[javaAddict]

You could use the time in millis and take the last digit:
System.currentMillis(); if I remember correct the method.

[masijade]

Why don't you look at the source code for nextDouble (or some other method) of the java.util.Random class?

[jwenting]

You could use the time in millis and take the last digit:
System.currentMillis(); if I remember correct the method.

that would be using "any API".
In fact the mere act of creating a class has you using "any API".

[jinternalframe]

You can use the java.util.Random class for this, just make sure you seed the class with System.currentTimeMillis() to make sure you get a true random number, it can return a number of types. Give it a try.

[peter_budo]

You can use the java.util.Random class for this, just make sure you seed the class with System.currentTimeMillis() to make sure you get a true random number, it can return a number of types. Give it a try.

Please read all the posts before you reply! Question was

Can anyone pls help me to generate random numbers without using any API???

[jinternalframe]

Please read all the posts before you reply! Question was

Oops! My bad.

You can try this, as random number generation is a very tricky task, which i am sure most programmers cannot do themselves. I got this from the net.

/*
 * Copyright 2005, 2007 Nick Galbreath -- nickg [at] modp [dot] com
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
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 *   notice, this list of conditions and the following disclaimer.
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 *   Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 *   Neither the name of the modp.com nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * http://www.opensource.org/licenses/bsd-license.php
 */
package com.modp.random;

/**
 * Re-implemtation of the PRNG from java.util.Random.
 *
 * <p>This is a re-implementation of the random number generation
 * that is used in Sun's <code>java.util.Random</code>.  It is unsynchronized
 * and so it is about 2x faster.
 * </p>
 *
 * @author Nick Galbreath nickg [at] modp [dot] com
 * @version 1 -- 06-Jul-2005
 */
public class LinearSunJDK implements RandomGenerator {

    private long seed;
    private final static long multiplier = 0x5DEECE66DL;
    private final static long addend = 0xBL;
    private final static long mask = (1L << 48) - 1;

    /* Constructor, initializes seed with current time
     * 
     */
    public LinearSunJDK() {
	setSeed(System.currentTimeMillis());
    }

    public LinearSunJDK(final long seed) {
	setSeed(seed);
    }

    public void setSeed(long seed) {
        this.seed = (seed ^ multiplier) & mask;
    }

    /* (non-Javadoc)
     * @see com.modp.random.RandomGenerator#next(int)
     */
    public int next(int numBits) {
	seed = (seed * multiplier + addend) & mask;
	return (int)(seed >>> (48 - numBits));
    }
}

And also see

http://www.cs.gmu.edu/~sean/research/mersenne/MersenneTwister.java

[jwenting]

he'd still be using an API...
In fact he'd be using one if he wrote his own generator as well, he'd be using his own :)

[jinternalframe]

he'd still be using an API...
In fact he'd be using one if he wrote his own generator as well, he'd be using his own :)

?? Where's the API ?
Its just a suggestion for coding. Its a pretty complex algorithm to code. He will have to be a Mathematician to even understand it.

[jwenting]

anything's an API.
A method call constitutes using an API.
Defining a method constitutes creating an API.

So effectively he's saying he's to write something while using no methods, no classes, no nothing except basic math on primitives.

Of course, as you say, he's not going to succeed in that unless he's a mathematician.
But then, anyone who's seriously given such a homework assignment would be a student of mathematics.

Most likely the kiddo just didn't understand his assignment (or simply didn't read it at all) and wants us to do its homework for it like so many others of its kind.
It's in character, posting a single vague message and never getting back. Though it's not as much fun as many, who would come back and start spewing abuse at people telling them to do their own homework ;)