Many programming contest problems are somehow related Prime Numbers. Either we are required to check Prime Numbers, or we are asked to perform certain functions for all prime number between 1 to N. Example: Calculate the sum of all prime numbers between 1 and 1000000.

Java provides two function under java.math.BigInteger to deal with Prime Numbers.

**isProbablePrime(int certainty):**A method in BigInteger class to check if a given number is prime. For certainty = 1, it return true if BigInteger is prime and false if BigInteger is composite.

Below is Java program to demonstrate above function.

`// A Java program to check if a number is prime using` `// inbuilt function` `import java.util.*;` `import java.math.*;` ` ` `class` `CheckPrimeTest` `{` ` ` `//Function to check and return prime numbers` ` ` `static` `boolean checkPrime(` `long` `n)` ` ` `{` ` ` `// Converting long to BigInteger` ` ` `BigInteger b = ` `new` `BigInteger(String.valueOf(n));` ` ` ` ` `return` `b.isProbablePrime(1);` ` ` `}` ` ` ` ` `// Driver method` ` ` `public` `static` `void` `main (String[] args)` ` ` `throws java.lang.Exception` ` ` `{` ` ` `long` `n = 13;` ` ` `System.out.println(checkPrime(n));` ` ` `}` `}` |

Output:

true

**nextProbablePrime()**: Another method present in BigInteger class. This functions returns the next Prime Number greater than current BigInteger.

Below is Java program to demonstrate above function.

`// Java program to find prime number greater than a` `// given number using built in method` `import java.util.*;` `import java.math.*;` ` ` `class` `NextPrimeTest` `{` ` ` `// Function to get nextPrimeNumber` ` ` `static` `long` `nextPrime(` `long` `n)` ` ` `{` ` ` `BigInteger b = ` `new` `BigInteger(String.valueOf(n));` ` ` `return` `Long.parseLong(b.nextProbablePrime().toString());` ` ` `}` ` ` ` ` `// Driver method` ` ` `public` `static` `void` `main (String[] args)` ` ` `throws java.lang.Exception` ` ` `{` ` ` `long` `n = 14;` ` ` `System.out.println(nextPrime(n));` ` ` `}` `}` |

Output:

17

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