The method **gcd(long a, long b)** of Guava’s LongMath Class returns the greatest common divisor of two parameters a and b.

**Syntax:**

public static long gcd(long a, long b)

**Parameters: **This method accepts two parameters a and b of the long type of whose GCD is to be found.

**Return Type: **This method returns the largest positive **long value** that divides both of the parameters passed to the function.

**Exceptions: **The method gcd(long a, long b) throws * IllegalArgumentException* if a is negative or b is negative.

**Note: **If a and b both are zero, the method returns zero.

**Example 1:**

`// Java code to show implementation of` `// gcd(long a, long b) method of Guava's` `// LongMath class` ` ` `import` `java.math.RoundingMode;` `import` `com.google.common.math.LongMath;` ` ` `class` `GFG {` ` ` ` ` `// Driver code` ` ` `public` `static` `void` `main(String args[])` ` ` `{` ` ` `long` `a1 = ` `14` `;` ` ` `long` `b1 = ` `70` `;` ` ` ` ` `// Using gcd(long a, long b) method` ` ` `// of Guava's LongMath class` ` ` `long` `ans1 = LongMath.gcd(a1, b1);` ` ` ` ` `System.out.println(` `"GCD of "` `+ a1` ` ` `+ ` `" and "` `+ b1` ` ` `+ ` `" is "` `+ ans1);` ` ` ` ` `long` `a2 = ` `23` `;` ` ` `long` `b2 = ` `15` `;` ` ` ` ` `// Using gcd(long a, long b) method` ` ` `// of Guava's LongMath class` ` ` `long` `ans2 = LongMath.gcd(a2, b2);` ` ` ` ` `System.out.println(` `"GCD of "` `+ a2` ` ` `+ ` `" and "` `+ b2` ` ` `+ ` `" is "` `+ ans2);` ` ` `}` `}` |

**Output:**

GCD of 14 and 70 is 14 GCD of 23 and 15 is 1

**Example 2:**

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

**Output:**

java.lang.IllegalArgumentException: a (-5) must be >= 0

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