在Java中生成隨機(jī)數(shù)有三種主要方法。第一，使用Random類生成整數(shù)、雙精度數(shù)或特定范圍內(nèi)的數(shù)值，例如rand.nextInt(100)生成0到99的整數(shù)；第二，使用Math.random()生成0.0到1.0之間的雙精度數(shù)，并可通過乘法和強(qiáng)制類型轉(zhuǎn)換生成整數(shù)；第三，使用Java 8及以上版本的ThreadLocalRandom，例如ThreadLocalRandom.current().nextInt(1, 101)生成1到100的整數(shù)，其在多線程環(huán)境中性能更優(yōu)。根據(jù)具體需求和Java版本選擇合適的方法即可。

To generate a random number in Java, you have a few straightforward options depending on what kind of number you need — whether it's an integer, a double, or within a specific range. The most common tools are the Random class and Math.random(). Here's how to use them effectively.

Using the Random Class for More Control

The Random class in the java.util package gives you more flexibility. It lets you generate different types of random values — integers, doubles, booleans, etc.

Here’s a basic example:

import java.util.Random;

Random rand = new Random();
int randomNumber = rand.nextInt(100); // generates a number between 0 (inclusive) and 100 (exclusive)

If you want a number within a specific range, say between 10 and 50:

int min = 10;
int max = 50;
int range = max - min   1;
int randomNumberInRange = rand.nextInt(range)   min;

This approach is useful when you're building things like random IDs, game mechanics, or sample data.

Using Math.random() for Quick and Simple Needs

If you just need a quick random double between 0.0 (inclusive) and 1.0 (exclusive), Math.random() is the simplest way to go.

Example:

double randomDouble = Math.random();

To get an integer from it, say between 1 and 10:

int randomInt = (int)(Math.random() * 10)   1;

• This method is good for simple use cases
• It doesn’t require creating an object like Random does
• It’s slightly less flexible but perfectly fine for small tasks

Generating Random Numbers in Java 8 with ThreadLocalRandom

If you're using Java 8 or newer, ThreadLocalRandom is a modern alternative that performs better in multi-threaded environments.

Here’s how you use it:

import java.util.concurrent.ThreadLocalRandom;

int randomNum = ThreadLocalRandom.current().nextInt(1, 101); // between 1 and 100 inclusive

• It avoids the need to create a Random instance
• It's faster and more efficient in concurrent code
• You can still use it easily in single-threaded code

This is a good default choice if you're on Java 8 or higher and don’t have a reason to use Math.random() or Random.

基本上就這些。 Depending on your use case — and your Java version — any of these methods can work well. If you're working in a loop or generating many random values, Random or ThreadLocalRandom are better choices. For one-off values, Math.random() is quick and easy.

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