Rounding using Java's Math.round() function

Use Java's Math.round() function to round to integers

In programming, we often encounter situations where we need to round numbers. Java provides the round() function in the Math class, which can help us implement rounding operations. This article will introduce the usage of Math.round() function and provide some code examples.

Math.round() function is one of the commonly used functions in Java for rounding. Its return value type is long, which can round a floating point number or a double type value to the nearest integer. The following is the prototype of the Math.round() function:

public static long round(double value)
public static int round(float value)

The parameter value is the value to be rounded , the return value is the nearest integer.

Next, let’s look at some specific examples.

Example 1: Rounding floating point numbers

public class Main {

public static void main(String[] args) {
    double num1 = 2.56;
    double num2 = 5.87;

    long roundedNum1 = Math.round(num1);
    long roundedNum2 = Math.round(num2);

    System.out.println("num1的四舍五入结果为：" + roundedNum1);
    System.out.println("num2的四舍五入结果为：" + roundedNum2);
}

}

Run the above code, the output results are as follows:

The rounding result of num1 is: 3
The rounding result of num2 is: 6

Example 2: Round floating point numbers and cast the result to int type

public class Main {

public static void main(String[] args) {
    double num = 3.14;
    int roundedNum = (int) Math.round(num);

    System.out.println("num的四舍五入结果为：" + roundedNum);
}

}

Run the above code, the output result is as follows:

The rounding result of num is: 3

Things to note Yes, even if the result is cast to int type, the Math.round() function will still return a long result. Therefore, the cast must be done before storing the result in an int type variable.

Example 3: Round floating point numbers and retain the specified number of decimal places

import java.text.DecimalFormat;

public class Main {

public static void main(String[] args) {
    double num = 3.1415926;

    DecimalFormat df = new DecimalFormat("#.##");
    String roundedNum = df.format(num);

    System.out.println("num的四舍五入结果为：" + roundedNum);
}

}

Run the above code, the output result is as follows:

The rounded result of num is: 3.14

In example 3, we used the DecimalFormat class to retain the specified of decimal places. Among them, the formatting mode "#.##" means keeping two decimal places. By converting the result to type String we can be more flexible with the number of decimal places.

Summary:

This article introduces how to use Java's Math.round() function for rounding. Through the demonstration of several examples, we can have a good grasp of this commonly used numerical processing function. In actual development, if you need to perform rounding operations on floating-point numbers or double types, you can consider using the Math.round() function, which can easily help us achieve rounding requirements.

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