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# Java Guava | gcd(int a, int b) method of IntMath Class

• Last Updated : 28 Jan, 2019

The method gcd(int a, int b) of Guava’s IntMath class returns the greatest common divisor of a, b.

Syntax :

```public static int gcd(int a, int b)

Where a and b are integers.
```

Return Value : Greatest common divisor of integers a and b.

Exceptions : The method gcd(int a, int b) throws IllegalArgumentException if a < 0 or b < 0.

Example 1 :

 `// Java code to show implementation of``// gcd(int a, int b) method of Guava's``// IntMath class``import` `java.math.RoundingMode;``import` `com.google.common.math.IntMath;`` ` `class` `GFG {`` ` `    ``// Driver code``    ``public` `static` `void` `main(String args[])``    ``{``        ``int` `a1 = ``64``;``        ``int` `b1 = ``36``;`` ` `        ``// Using gcd(int a, int b) method``        ``// of Guava's IntMath class``        ``int` `ans1 = IntMath.gcd(a1, b1);`` ` `        ``System.out.println(``"GCD of a1 & b1 is: "``                           ``+ ans1);`` ` `        ``int` `a2 = ``23``;``        ``int` `b2 = ``15``;`` ` `        ``// Using gcd(int a, int b) method``        ``// of Guava's IntMath class``        ``int` `ans2 = IntMath.gcd(a2, b2);`` ` `        ``System.out.println(``"GCD of a2 & b2 is: "``                           ``+ ans2);``    ``}``}`
Output:
```GCD of a1 & b1 is: 4
GCD of a2 & b2 is: 1
```

Example 2 :

 `// Java code to show implementation of``// gcd(int a, int b) method of Guava's``// IntMath class``import` `java.math.RoundingMode;``import` `com.google.common.math.IntMath;`` ` `class` `GFG {`` ` `    ``// Driver code``    ``public` `static` `void` `main(String args[])``    ``{``        ``int` `a1 = -``5``;``        ``int` `b1 = ``15``;`` ` `        ``try` `{``            ``// Using gcd(int a, int b) method``            ``// of Guava's IntMath class``            ``// This should throw "IllegalArgumentException"``            ``// as a1 < 0``            ``int` `ans1 = IntMath.gcd(a1, b1);``        ``}``        ``catch` `(Exception e) {``            ``System.out.println(e);``        ``}``    ``}``}`
Output:
```java.lang.IllegalArgumentException: a (-5) must be >= 0
```

Note: The method returns 0 if a == 0 && b == 0.

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