# Java.math.BigInteger.probablePrime() method in Java

Last Updated : 04 Dec, 2018

Prerequisite : BigInteger Basics

The probablePrime() method will return a Biginteger of bitLength bits which is prime. bitLength is provided as parameter to method probablePrime() and method will return a prime BigInteger of bitLength bits. The probability that a BigInteger returned by this method is composite and does not exceed 2^-100.

Syntax:

`public static BigInteger probablePrime(int bitLength, Random rnd)`

Parameters: This method accepts two parameters as shown in the above syntax and described below.

• bitLength – bitLength of the returned BigInteger.
• rnd – source of random bits used to select candidates to be tested for primality.

Return Value: This method returns a BigInteger of bitLength bits that is probably prime.

Exception:

• ArithmeticException – if bitLength < 2.

Below program illustrate the probablePrime() method:

 `import` `java.math.*; ` `import` `java.util.Random; ` `import` `java.util.Scanner; ` ` `  `public` `class` `GFG { ` ` `  `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` ` `  `        ``Scanner sc = ``new` `Scanner(System.in); ` ` `  `        ``// create a BigInteger object ` `        ``BigInteger biginteger; ` ` `  `        ``// create a integer value for bitLength ` `        ``int` `length = ``4``; ` ` `  `        ``// create a random object ` `        ``Random random = ``new` `Random(); ` ` `  `        ``// call probablePrime method to find next probable prime ` `        ``// whose bit length is equal to bitLength provided as parameter. ` `        ``biginteger = BigInteger.probablePrime(length, random); ` ` `  `        ``String result = ``"ProbablePrime whose bit length is "` `                        ``+ length + ``" = "` `+ biginteger; ` ` `  `        ``// print result value ` `        ``System.out.println(result); ` `    ``} ` `}`

Output:

```ProbablePrime whose bit length is 4 = 13
```

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