Java - Discard some elements of a stream

Introduction

To discard some elements of a stream, use the skip operation.

The skip(long n) method of the Stream interface discards the first n elements of the stream.

This is an intermediate operation.

The following code uses skip() method to print five prime numbers, skipping the first 100 prime numbers:

Demo

import java.util.stream.Stream;

public class Main {
  public static void main(String[] args) {
    Stream.iterate(2L, PrimeUtil::next)
    .skip(100)//from w w w. j a  va2 s .co m
    .limit(5)
    .forEach(System.out::println);
  }
}

class PrimeUtil {
  private long lastPrime = 0L;

  // Computes the prime number after the last generated prime
  public long next() {
    lastPrime = next(lastPrime);
    return lastPrime;
  }

  // Computes the prime number after the specified number
  public static long next(long after) {
    long counter = after;

    // Keep looping until you find the next prime number
    while (!isPrime(++counter))
      ;

    return counter;
  }

  // Checks if the specified number is a prime number
  public static boolean isPrime(long number) {
    // <= 1 is not a prime number
    if (number <= 1) {
      return false;
    }

    // 2 is a prime number
    if (number == 2) {
      return true;
    }

    // Even numbers > 2 are not prime numbers
    if (number % 2 == 0) {
      return false;
    }

    long maxDivisor = (long) Math.sqrt(number);
    for (int counter = 3; counter <= maxDivisor; counter += 2) {
      if (number % counter == 0) {
        return false;
      }
    }

    return true;
  }
}

Java - Discard some elements of a stream

Introduction

Demo

Result

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