RandomTools Tutorial

RandomTools is a utility class for generating various types of random values, including numbers, strings, and UUIDs (with version 7 support).

Main Features

1. Thread-safe random generation: Uses ThreadLocalRandom for high performance
2. Explicit random sources: Exposes both SecureRandom and ordinary Random; choose according to the use case
3. Multiple random value generation: Supports numbers, strings, UUIDv7, etc.
4. Time-ordered UUIDs: UUIDv7 provides better locality than random UUIDs

Number Random Generation

1. Generate Six-Digit Numbers

// Generate a six-digit random number (100000-999999)
int number = RandomTools.generateNumber();
System.out.println(number); // e.g.: 456789

2. Generate Numbers with Specified Digits

// Generate random numbers with specified digit count
int threeDigit = RandomTools.generateNumber(3); // 100-999
int fourDigit = RandomTools.generateNumber(4); // 1000-9999

System.out.println(threeDigit); // e.g.: 567
System.out.println(fourDigit);  // e.g.: 3456

The digit count must be between 1 and 9; other values throw IllegalArgumentException.

String Random Generation

1. Generate Six-Character Random String

// Generate a six-character alphanumeric random string
String randomStr = RandomTools.generateRandomString();
System.out.println(randomStr); // e.g.: aB3xY9

The requested string length must be positive. These strings use ThreadLocalRandom and are not intended as passwords, tokens, or cryptographic secrets.

2. Generate Random String with Specified Length

// Generate random strings with specified length
String shortStr = RandomTools.generateRandomString(3);
String longStr = RandomTools.generateRandomString(10);

System.out.println(shortStr); // e.g.: Xy2
System.out.println(longStr);  // e.g.: AbC3dE5fGh

UUID Generation

1. Generate UUIDv7

// Generate UUID version 7 (time-ordered)
UUID uuid = RandomTools.uuid();
System.out.println(uuid); // version field is 7

2. Generate UUIDv7 String Without Hyphens

// Generate UUID string without hyphens
String uuidStr = RandomTools.uuidStr();
System.out.println(uuidStr); // e.g.: 550e8400e29b41d4a716446655440000

3. View Timestamp of UUID

// Get timestamp information from UUIDv7
String uuidString = RandomTools.uuidStr();
Date timestamp = RandomTools.showTime(uuidString);
System.out.println(timestamp); // e.g.: Wed Oct 25 14:30:45 CST 2023

Notes

1. All generation methods are static and can be called directly through the class name
2. Number generation uses ThreadLocalRandom to ensure thread safety and performance
3. UUIDv7 is time-ordered and has better database indexing performance
4. String generation uses a fixed alphanumeric character pool
5. The current UUIDv7 random portion uses java.util.Random; UUIDs are suitable as identifiers, not as security tokens.