The **multiplyHigh(long x, long y)** method of **Math class** is used to return the most significant 64 bits from the 128-bit product of two 64-bit factors. This method takes two long values as input and a long is a 64-bit number. This method multiplies both long values and returns the most significant 64 bits from the product result which can be 128 bit long.

**Syntax:**

public static long multiplyHigh(long x, long y)

**Parameters:** This method accepts two long **x, y** as parameter where x and y are argument we want to multiply.

**Return Value:** This method returns the most significant 64 bits long value from the 128-bit product of two 64-bit numbers**i.e. X * Y**.

**Note:** This method was added in** JDK 9. Hence it wont run in Online IDE.**

Below programs illustrate the multiplyHigh() method:

**Program 1:**

`// Java program to demonstrate` `// multiplyHigh() method of Math class` ` ` `public` `class` `GFG {` ` ` ` ` `// Main method` ` ` `public` `static` `void` `main(String[] args)` ` ` `{` ` ` ` ` `// two long values` ` ` `long` `a = 45267356745l, b = 45676556735l;` ` ` ` ` `// apply multiplyHigh method` ` ` `long` `c = Math.multiplyHigh(a, b);` ` ` ` ` `// print result` ` ` `System.out.println(a + ` `" * "` ` ` `+ b + ` `" = "` ` ` `+ c);` ` ` `}` `}` |

**Output:**

45267356745 * 45676556735 = 112

**Program 2:** Multiplying two long contains Long.MAX values.

`// Java program to demonstrate` `// multiplyHigh() method of Math class` ` ` `public` `class` `GFG {` ` ` ` ` `// Main method` ` ` `public` `static` `void` `main(String[] args)` ` ` `{` ` ` ` ` `// two Integer values` ` ` `long` `a = Long.MAX_VALUE, b = Long.MAX_VALUE;` ` ` ` ` `// apply multiplyHigh method` ` ` `long` `c = Math.multiplyHigh(a, b);` ` ` ` ` `// print result` ` ` `System.out.println(a + ` `" * "` ` ` `+ b + ` `" = "` `+ c);` ` ` `}` `}` |

**Output:**

9223372036854775807 * 9223372036854775807 = 4611686018427387903

References: https://docs.oracle.com/javase/10/docs/api/java/lang/Math.html#multiplyHigh(long, long)

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