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

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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