How to generate random numbers using Random function in Java

When writing Java programs, we often need to generate random numbers for various purposes, such as test data, password generation, etc. Java provides the Random class to implement the function of generating random numbers. This article will introduce how to use the Random function in Java to generate random numbers.

1. Import Random class

Before using the Random class, we need to import it, which can be imported using the import statement at the beginning of the code. The sample code is as follows:

import java.util.Random;

2. Creating a Random object

Before using the Random class, we need to create a Random object first. You can create a Random object whose random seed is the current time of the system through the parameterless constructor, or you can create a Random object by specifying a seed. The sample code is as follows:

Random random = new Random(); // 创建一个随机种子为系统当前时间的Random对象 long seed = 12345l; // 指定一个种子 Random random = new Random(seed); // 创建一个指定种子的Random对象

3. Generate random numbers

Once the Random object is created, we can generate random numbers through its methods. The following are several ways to generate random numbers:

Generate a random integer

You can use the nextInt() method to generate a random integer. The parameters of this method can specify the range of random numbers to be generated, but if no parameters are specified, a random integer will be generated. The sample code is as follows:

int randomInt = random.nextInt(); // 生成一个随机的整数 int randomIntInRange = random.nextInt(100); // 生成一个0-99之间的整数

Generate a random long integer

You can use the nextLong() method to generate a random long integer. This method has no parameters. The sample code is as follows:

long randomLong = random.nextLong(); // 生成一个随机的长整数

Generate a random floating point number

You can use the nextFloat() method to generate a random floating point number. The range of this floating point number is [0, 1). The sample code is as follows:

float randomFloat = random.nextFloat(); // 生成一个随机的浮点数

Generate a random double-precision floating-point number

You can use the nextDouble() method to generate a random double-precision floating-point number. The range of this double-precision floating-point number is [0 , 1). The sample code is as follows:

double randomDouble = random.nextDouble(); // 生成一个随机的双精度浮点数

Generate a Boolean value

You can use the nextBoolean() method to generate a random Boolean value. This method has no parameters. The sample code is as follows:

boolean randomBoolean = random.nextBoolean(); // 生成一个随机的布尔值

4. Generate a random number within the specified range

If we need to generate a random number within the specified range, we can first generate a random number, and then Process it to suit our needs. The following are several ways to generate random numbers within a specified range:

Generate an integer within a specified range

You can use the nextInt(int bound) method to generate a random integer with a range of [0, bound). The sample code is as follows:

int randomIntInRange = random.nextInt(100); // 生成一个0-99之间的整数

We can also use some mathematical operations to generate an integer within a specified range. The sample code is as follows:

int min = 10; int max = 20; int randomIntInRange = random.nextInt(max - min + 1) + min; // 生成一个10-20之间的整数

Generate a floating point number within a specified range

You can generate a floating point number within a specified range as needed, you can use the following code:

double min = 1.0; double max = 2.0; double randomDoubleInRange = min + (max - min) * random.nextDouble(); // 生成一个1.0-2.0之间的浮点数

5. Summary

This article introduces how to use the Random function in Java to generate random numbers. We can create a Random object whose random seed is the current time of the system through the parameterless constructor, or we can create a Random object by specifying a seed. The methods of the Random object can generate random numbers such as integers, long integers, floating point numbers, and Boolean values. We can also generate random numbers within a specified range as needed.

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