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genopri-shcs/project/CertifiedInstitution/CertifiedInstitution/src/Crypto/PrimeGenerator.java
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PrimeGenerator.java
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/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package Crypto;
import java.math.BigInteger;
import java.util.Vector;
/**
*
* @author raisaro
*/
public class PrimeGenerator {
private BigInteger gen; // This number occurs just before the
// smallest generated prime.
/**
* Initializes the generator.
*/
public PrimeGenerator() {
gen = BigInteger.ONE;
}
/**
* Obtains a specified number of primes.
*
* @param start No primes will be returned whose values are less than this.
* @param num The number of primes to generate.
*
* @return A list of prime integers.
*/
public Vector< Long > getPrimes( long start, int num ) {
Vector< Long > p; // The primes found.
p = new Vector< Long >( num );
gen = BigInteger.valueOf( start - 1 );
for( int i = 0; i < num; i++ ) {
gen = gen.nextProbablePrime();
p.add( gen.longValue() );
}
return p;
}
/**
* Obtains a specified number of primes.
*
* @param digits The primes must have at least this number of digits.
* @param num The number of primes to generate.
*
* @return A list of prime numbers.
*/
public Vector< BigInteger > getBigPrimes( int digits, int num ) {
Vector< BigInteger > p; // The primes found.
String start; // Primes must be greater than this number.
p = new Vector< BigInteger >( num );
start = String.valueOf( '1' );
for( int i = 1; i < digits; i++ ) {
start = start.concat( "0" );
}
gen = new BigInteger( start );
for( int i = 0; i < num; i++ ) {
gen = gen.nextProbablePrime();
p.add( gen );
}
return p;
}
/**
* Obtains all primes within a range of values. The lower and
* upper bound are inclusive, so they will appear in the list of
* primes if they are prime values.
*
* @param lb Lower bound of the range.
* @param ub Upper bound of the range.
*
* @return A list of prime integers.
*/
public Vector< Long > getPrimesBetween( long lb, long ub ) {
Vector< Long > p; // The primes found.
BigInteger stop; // Indicates when to stop generating values.
p = new Vector< Long >();
gen = BigInteger.valueOf( lb - 1 );
stop = BigInteger.valueOf( ub );
while( gen.compareTo( stop ) <= 0 ) {
gen = gen.nextProbablePrime();
p.add( gen.longValue() );
}
return p;
}
}
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