Gets the prime numbers for the given quantity. - Java java.lang

Java examples for java.lang:Math Prime Number

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Description

Gets the prime numbers for the given quantity.

Demo Code

/**// ww w . ja  v  a2  s . co m
 * The MIT License
 *
 * Copyright (C) 2007 Asterios Raptis
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
//package com.java2s;

public class Main {
    /**
     * Gets the prime numbers for the given quantity.
     * 
     * @param quantity
     *            The quantity.
     * @return An array from prime numbers.
     */
    public static int[] getPrimeNumbers(final int quantity) {

        final int[] primes = new int[quantity];

        int i = 0;
        int number = 2;

        while (i < quantity) {

            final boolean isPrime = isPrime(number);
            if (isPrime) {
                primes[i++] = number;
            }
            number++;
        }

        return primes;
    }

    /**
     * Checks if the given int is a prime number.
     * 
     * @param n
     *            The int to check.
     * @return Returns true if the int is a prime number otherwise false.
     */
    static boolean isPrime(final int n) {
        int mod = 1;
        for (int i = 2, end = (int) Math.sqrt(n); i <= end && mod != 0; i++) {
            mod = n % i;
        }
        return mod != 0;
    }
}

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