Java Math round() Method (original) (raw)

Last Updated : 13 May, 2025

The **Math.round() method is a part of the **java.lang.Math library. This method returns the closest long to the argument. In this article, we are going to discuss how this method works for regular values and for special cases.

**Note: If the fraction is less than 0.5 then the number is rounded down and if the fraction is more than 0.5 then the number is rounded up.

**Special Cases:

If the argument is NaN, the method will return **zero.
If the argument is **negative infinity or any value less than or equal to the value of an **Long.MIN_VALUE, the method will return an **Long.MIN_VALUE.
If the argument is **positive infinity or any value greater than or equal to **Long.MAX_VALUE, the method will return **Long.MAX_VALUE.

These special cases make sure that the **Math.round() methods work correctly.

Syntax of round() Method

public static long round(float val)

**Parameter: This method takes a single parameter **val of type **float, which is a float that will be rounded to nearest **integer.
**Return Type: This method returns the closest rounded value as **long.

Now, we are going to discuss some examples for better understanding and clarity.

Examples of Java Math round() Method

**Example 1: In this example, we will see the **basic usage of Math.round() method.

Java `

// Java program to demonstrate the working // of Math.round() method import java.lang.Math;

class Geeks {

// driver code
public static void main(String args[]) {
    
    // float numbers
    float x = 4567.9874f;

    // find the closest long for these floats
    System.out.println(Math.round(x)); 
}

}

**Explanation: Here, we rounded the value of **x to the nearest long.

**Example 2: In this example, we will see how the round() method handles all the special cases.

Java `

// Java program to demonstrate the working // of Math.round() method for special cases import java.lang.Math;

class Geeks {

// driver code
public static void main(String args[]) {
    
    // float numbers
    float x = 4567.9874f;

    // find the closest long for these floats
    System.out.println(Math.round(x));

    float y = -3421.134f;

    // find the closest long for these floats
    System.out.println(Math.round(y));

    double p = Double.POSITIVE_INFINITY;

    // returns the Long.MAX_VALUE value when 
    System.out.println(Math.round(p));
}

}

Output

4568 -3421 9223372036854775807

**Explanation: When the input is **Double.POSITIVE_INFINITY, **Math.round() returns **Long.MAX_VALUE, which is **9223372036854775807.