Java 下計算質數的多線程跟單線程執行代碼分析

Java 下計算質數的多線程跟單線程執行代碼分析

public abstract class AbstractPrimeFinder {
public boolean isPrime(final int number) {
if (number <= 1)
return false;
for (int i = 2; i <= Math.sqrt(number); i++)
if (number % i == 0)
return false;
return true;
}

public int countPrimesInRange(final int lower, final int upper) {
int total = 0;
for (int i = lower; i <= upper; i++)
if (isPrime(i))
total++;
return total;
}

public void timeAndCompute(final int number) {
final long start = System.nanoTime();
final long numberOfPrimes = countPrimes(number);
final long end = System.nanoTime();
System.out.printf("Number of primes under %d is %d\n", number,
numberOfPrimes);
System.out.println("Time (seconds) taken is " + (end - start) / 1.0e9);
}

public abstract int countPrimes(final int number);
}

public class SequentialPrimeFinder extends AbstractPrimeFinder {
public int countPrimes(final int number) {
return countPrimesInRange(1, number);
}

public static void main(final String[] args) {
new SequentialPrimeFinder().timeAndCompute(10000000);
}
}