# Java.math.BigInteger.isProbablePrime() Method

## Description

The java.math.BigInteger.isProbablePrime(int certainty) returns true if this BigInteger is probably prime, false if it's definitely composite. If certainty is ≤ 0, true is returned.

## Declaration

Following is the declaration for java.math.BigInteger.isProbablePrime() method.

```public boolean isProbablePrime(int certainty)
```

## Parameters

certainty − a measure of the uncertainty that the caller is willing to tolerate: if the call returns true the probability that this BigInteger is prime exceeds (1 - 1/2certainty). The execution time of this method is proportional to the value of this parameter.

## Return Value

This method returns true if this BigInteger is probably prime, false if it's definitely composite.

NA

## Example

The following example shows the usage of math.BigInteger.isProbablePrime() method.

```package com.tutorialspoint;

import java.math.*;

public class BigIntegerDemo {

public static void main(String[] args) {

// create 3 BigInteger objects
BigInteger bi1, bi2, bi3;

// create 3 Boolean objects
Boolean b1, b2, b3;

// assign values to bi1, bi2
bi1 = new BigInteger("7");
bi2 = new BigInteger("9");

// perform isProbablePrime on bi1, bi2
b1 = bi1.isProbablePrime(1);
b2 = bi2.isProbablePrime(1);
b3 = bi2.isProbablePrime(-1);

String str1 = bi1+ " is prime with certainity 1 is " +b1;
String str2 = bi2+ " is prime with certainity 1 is " +b2;
String str3 = bi2+ " is prime with certainity -1 is " +b3;

// print b1, b2, b3 values
System.out.println( str1 );
System.out.println( str2 );
System.out.println( str3 );
}
}
```

Let us compile and run the above program, this will produce the following result −

```7 is prime with certainity 1 is true
9 is prime with certainity 1 is false
9 is prime with certainity -1 is true
```
java_math_biginteger.htm